Triangle Definition and 1000 Threads

  1. C

    Calculating the Width of a Triangle at Position x

    Homework Statement Given an isosceles triangle - Length = L - Uniform Density = ρ - Width Varies from 0 at x = 0 to a at x = L I attached a picture of it. Homework Equations Have to show the width at position x is given by (a/L)x The Attempt at a Solution Now it is...
  2. J

    Drawing a right triangle to simpliy the given expressions

    1. Homework Statement Sin(sec^-1(sqrt(x^2+16)/4)) 2. Homework Equations 3. The Attempt at a Solution I did the math and ended up getting x^2-1 as the opposite, but the answers on the back of the book say other wise.
  3. J

    Drawing a right triangle to simply the given expressions

    Homework Statement Cos(Tan^-1(x)) Homework Equations The Attempt at a Solution Dont know how drawing a right triangle would do anything, don't know what to plug in.
  4. V

    Triangle integral ∫∫dxdyf(x*y) how to reduce to one dimension?

    I meet with a triangle integral where x+y≤1, and function is dependant only on x*y. I am wondering if there any possibility to relate ∫∫dxdyf(x*y)=∫d(x*y)f(x*y)g(x*y) or something similar? Or maybe there are some assumptions needed to relate like this?
  5. H

    Striking the End of a Triangle in Space

    Homework Statement http://img221.imageshack.us/img221/4861/figure1h.png Mod note: Fixed the image link.[/color] Consider the rigid object shown in this image. Four masses lie at the points shown on a rigid isosceles right triangle with hypotenuse length 4a. The mass at the right angle...
  6. L

    Geometry Triangle Congruence - Should be easy?

    Geometry Triangle Congruence - **Edited to include diagram** Homework Statement Hi! The three simple geometry problems are in the attached photo. Sorry if they're difficult to read. I haven't seen this information in so long, and could use some help. :D Can you use the given information...
  7. F

    MHB Perpendicular vectors, triangle, tetrahedron

    Prove that, if (c - b).a = 0 and (c - a).b = 0, then (b - a).c = 0. Show that this can be used to prove the following geometric results: a. The lines through the vertices of a triangle ABC perpendicular to the opposite sides meet in a point. b. If the tetrahedron OABC has two pairs of...
  8. F

    Perpendicular vectors, triangle, tetrahedron

    Prove that, if (c - b).a = 0 and (c - a).b = 0, then (b - a).c = 0. Show that this can be used to prove the following geometric results: a. The lines through the vertices of a triangle ABC perpendicular to the opposite sides meet in a point. b. If the tetrahedron OABC has two pairs of...
  9. S

    Area of a Triangle Word Problem

    Homework Statement If the height of a triangle is five centimeters less than the length of its base and if the area of the triangle is 52 cm^2, find the base and the height.Homework Equations N/A The Attempt at a Solution height = h-5 base = h A=(bh)/2 52=(h(h-5)/2 52=(h^2-5h)/2 104=h^2-5h...
  10. L

    Electric Fields in Equilateral Triangle

    Homework Statement A point charge q = +2.0 µC is placed at each corner of an equilateral triangle with sides 0.23 m in length. What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle? 3. I want to know if I did this correctly, or totally...
  11. B

    Triangle and dot product to find angle

    Vector A and vector B are expressed in component form. A = [2.32,-5.16,7.88] B = [-1.12,3.45,-12.8] The standard arrow representation of these vectors and that of can be arranged to form a triangle in a plane that represents the geometric equivalent of the subtraction operation. The...
  12. T

    Triangle Inequality for a Metric

    Homework Statement Prove the triangle inequality for the following metric d d\big((x_1, x_2), (y_1, y_2)\big) = \begin{cases} |x_2| + |y_2| + |x_1 - y_1| & \text{if } x_1 \neq y_1 \\ |x_2 - y_2| & \text{if } x_1 = y_1 \end{cases}, where x_1, x_2, y_1, y_2 \in \mathbb{R}...
  13. S

    Is the interval the height of the triangle?

    A FAQ is why the spacetime interval has a minus sign. A geometrical answer is that the interval is always the shortest path (the straight line) between two points. If we talk about spatial points, that interval is the hypotenuse of a right angle triangle, whose sides are the projections of...
  14. T

    Using Triangle Inequality to find a magnitude

    Homework Statement Let a, x, and y be real numbers and let E > 0. Suppose that |x-a|< E and |y-a|< E. Use the Triangle Inequality to find an estimate for the magnitude |x-y|. Homework Equations The Triangle Inequality states that |a+b| <= |a| + |b| is valid for all real numbers a and...
  15. B

    Area of a circle within a circumscribed triangle

    If you have a triangle circumscribed around a circle, how do you find the area of that circle? Say that the triangle is an equilateral triangle with side length of 8 cm. I found the area of the triangle using Heron's formula: 16√3 cm^2. Apparently the answer is 16π/3 cm^2. I'm just confused...
  16. P

    MHB Area of an equilateral triangle

    Given an equilateral triangle ABC, P is any point inside it where PA = 3, PB = 4 and PC = 5. Find area of the triangle using the Law of Sines or Law of Cosines.
  17. D

    Addition of vectors with triangle vertices

    Homework Statement If A, B, and C are the vertices of a triangle, find the following. (A→B) + (B→C) + (C→A) The answer has to be given like this: _____ i + _____ j 2. Homework Equations (I think?) a+b=b+a a+(b+c)=(a+b)+c a+0=a a+(-a)=0 c(a+b)=ca+cb (c+d)a=ca+da (cd)a=c(da)...
  18. V

    Angled triangle ABC are x-1, x

    Homework Statement The length of the sides of the acute angled triangle ABC are x-1, x and x+1. BD is perpendicular to AC. Then CD-DA equals? Homework Equations cosine law The Attempt at a Solution
  19. J

    Area of Isosceles Triangle Problem

    Homework Statement An Isosceles triangle has two equal sides of length 10cm. Let x be the angle between the two equal sides. a. Express the area A of the triangle as a function of x in radians. b. Suppose that x is increasing at the rate of 10 degrees per minute. How fast is A changing...
  20. J

    Relative Error of Right Triangle Area

    Homework Statement Anyone mind checking my answer for me? The area of a right triangle with hypotenuse H is A=1/4H^2sin(2x) x is one of the acute angles. Use differentials to estimate the relative errors of the area if H = 4cm exactly and x is measured to be 30degrees with an error of...
  21. Z

    Double integral over triangle with known nodes

    I am wondering is there any general analytic solutions to the following integrals First moment of area Integral(xdxdy) Integral(ydxdy) Second moment of area) Integral(x^2dxdy) Integral(y^2dxdy) Integral(xydxdy) Over the triangle (x1,y1) (x2,y2) (x3,y3) thanks Wei
  22. B

    How Do Zener Diodes Impact a Triangle Wave Op-Amp Generator?

    Well another op-amp thread, while the other one is being cooked. http://pokit.org/get/a09120280ee2f6b6e3de7a99989b8bd9.jpg To speed you up, this is a triangle wave op amp generator. It generates a triangle wave at U2. In general I understand how the circuit works, but from the engineering...
  23. C

    Moment of inertia of triangle rotated about y axis

    Similar to my other thread https://www.physicsforums.com/showthread.php?t=557750 I think in this case I need to use triple integrals But what is the integrand and limits? Can someone please help me set it up? Here's all I know ∫∫∫dydx Please help I have my final next wednesday.
  24. L

    Triangle Angles: Find b & c with A-B-C given

    I am stuck on the job; I need to find the angles. It’s not an angle or side based triangle, just a right triangle. The lengths are known, A-B-C. What I need to know is the angles, a-b-c. So, a=90*, what formula could I use to find b, and c? Sorry, please make it easy enough for me to work it...
  25. P

    Understanding x(θ) and h(θ) in a Triangle Support Beam Problem

    Homework Statement I have attached the problem. I am confused about how they got x(θ) and h(θ). From the diagram it looks like they made it with reference to the triangular support beam. Why? Homework Equations The Attempt at a Solution
  26. J

    How to find the maximum area of a triangle?

    Homework Statement The hypotenuse of a right triangle has length of 10cm. Determine its maximum possible area. c= 10cm Homework Equations a^2 + b^2 = c^2 ? b*h*(1/2) The Attempt at a Solution just drew out the triangle so far, confused as to where to go from here i assume ill...
  27. S

    Inequality with Circle and Triangle in Euclidean Geometry

    Homework Statement Please see below... Homework Equations Please see below... The Attempt at a Solution Hi. This question is on geometry with circle and triangle. I am stuck only on 2 parts of the solution and not the whole solution... Thank you...
  28. J

    How Do You Calculate the Center of Mass for an Isosceles Triangle?

    Homework Statement Find the center of mass of a triangle with two equal sides of length a. The triangle's third side is length b and it has a uniform mass of M. Homework Equations R = \frac{1}{M} \int dm \vec{r} dm = \frac{M}{A} A = \frac{1}{2}base*height The Attempt at a Solution...
  29. S

    Finding centre of mass of an isosceles triangle

    Homework Statement Explorers in the jungle find an ancient monument in the shape of a large isosceles triangle. The monument is made from tens of thousands of small stone blocks of density 3 800 kg/m3. The monument is 15.7 m high and 64.8 m wide at its base and is everywhere 3.60 m thick...
  30. I

    Question 26.5: Triangle Circuit - Is My Drawing Correct?

    I am not sure how the configuration would look like if we add a voltage across these points. I have drawn out what I think it would look like after a potential is applied across Vab. My question is, is this drawing correct?? What about Vbc and Vac? This is question 26.5. And here is my...
  31. S

    Finding C_2 for Curve F in Triangle C

    Homework Statement F=<xy, x-y> and C is the triangle joining (1,0), (0,1) and (-1,0) in the clockwise direction. Homework Equations How do I have the second part of this curve? The Attempt at a Solution Apparently, there should only be a sum of two integrals. So I got that curve...
  32. J

    Where is the center of mass of a flat triangular plate with given dimensions?

    Find the x and y coordinates of the center of mass of a flat triangular plate of a height H =17.3cm and a base B = 10 Cm Homework Equations Area = A = 1/2bh x = 1/A ∫ x(f(x)) y = 1/A ∫ 1/2((f(x)^2) The Attempt at a Solution Area = 1/2(10)(17.3) = 86.5 f(x) = 17.3-1.73x or...
  33. shinnsohai

    ABC is an equilateral triangle

    Homework Statement Based on my understanding of the question the diagram should be like this ABC is an equilateral triangle with side 2a.Two circle are are drawn , with one of them crossing the points A,B and C.another circle crossess B and C with A as centre Prove that the area enclosed by...
  34. S

    Calculating Distance Between Inner & Outer Triangles

    Hi, I have an equilateral triangle and I put another equilateral triangle within it. The inner triangle has exactly half of the area of the outer triangle. As well, the inner triangle is placed in the centre of the outer triangle i.e. they both have the same central point. I want to...
  35. V

    Equilibrium and principle of triangle of forces

    1. Homework Statement A rope of 5m is fastened to two hooks 4m apart on a horizontal ceiling. To the rope is attached 10kg mass so that the segment of the rope are 3m and 2m.Compute the tension in the string 2. Homework Equations Sine rule, cosine rule 3. The Attempt at a Solution...
  36. F

    Calculating Probability of 2 Black Balls from 3-Ball Urn w/ Pascal Triangle

    if we toss 4 coins and we want to know the probability of having 3 heads we can easily calculate that using pascal triangle . I want to know if we have an Urn that contain 3 balls : 1 black , 1 red, 1 yellow. and we want to draw 3 balls , but when we draw the first ball we put it back in the...
  37. V

    Principle of triangle of forces

    Homework Statement A body of mass 700g hangs from the end of a long wire fixed to a high tree. A horizontal string attached to the body pulls it until the wire is at 30 degrees to the vertical.Find the tensions in the both the string and the wire Homework Equations Sine rule The...
  38. H

    Triangle Inequality for integrals proof

    Homework Statement What I want to show is this: ∫|x+y| ≤ ∫|x| + ∫|y| Homework Equations |x+y| ≤ |x| + |y| The Attempt at a Solution So I thought if I used the triangle inequality I could get to something along the lines of: Lets g belong to the real numbers ∫|x+y| =...
  39. P

    Ceq of 3 capacitors in a triangle

    I'm a little confused about this problem. I attached the pic. The solution manual states " capacitors C1 and C3 are in series with each other and in parallel with capacitor C2." I don't understand why it has to be C1 and C3 in series which is parallel with C2. Can't it also be C2&C3 in...
  40. O

    Triangle tangent to circle problem using derivatives

    Homework Statement A metal bar of length l in the figure below has one end attached at a point P to a circle ofradius a < l. Point Q at the other end can slide back and forth along the x–axis. (a) Find x as a function of θ (θ=angle POQ). (b) Assume the lengths are in centimeters and the...
  41. M

    Find the height of any triangle?

    Homework Statement I have the side lengths of a triangle. The base is 190 ft long, side A is 182 ft long and side B is 363 ft long. That's all I know. Homework Equations The Attempt at a Solution I know these side lengths are related somehow.
  42. I

    MATLAB [Matlab]Copy Lower Triangle of symmetric matrix to Upper Triangle(or visa versa)

    Hello all! I just had a question about combining elements of matrices. In the MATLAB documentation, there was a function called triu and tril that extracts the upper and lower components of a matrix, respectively. I was wondering if there was a way to copy the elements of the upper triangle...
  43. S

    Find curve with tangent and normal lines that create a triangle with given area

    Homework Statement Find the implicit equation of the curve that goes through the point (3, 1) and whose tangent and normal lines always form with the x-axis a triangle whose area is equal to the slope of the tangent line. Assume y` > 0 and y > 0. Homework Equations Hint: ∫( √(a^2 -...
  44. S

    Circles in an equilateral triangle.

    Homework Statement Three triangles are placed into a circle; The vertices of the triangle are tangential to each circle. How do you find the ratio of the area of the circles to that of the triangle? Homework Equations pi r^2, 1/2(b)(h), sqrt3/4 * a^2 (2r^2). The Attempt at a...
  45. O

    Area between Triangle and Rectangle

    Homework Statement Consider a large triangle, the tip is located at the origo x=0, it is sloped at an angle θ and -θ relative to the x-axis, relative to the x-axis, its dimensions in x can be considered infinite. A large stripe/strip/band is placed on top of the triangle but perpendicular to...
  46. E

    Finding the resultant of two vector of an oblique triangle

    Homework Statement A car travels 20.0 km due north and then 35.0 km in a direction 60.0° west of north. Using a graph, find the magnitude and direction of a single vector that gives the net effect of the car's trip. This vector is called the car's resultant displacement. I am...
  47. R

    Two primes in a Primitive Pythagorean Triangle

    Let's recall the Euclidean Rule for Pythagorean Triangles: Let (m,n) be co-prime natural numbers (m<n), then h := n^{2} + m^{2} e := 2 m n d := n^{2} - m^{2} = (n - m) * (n + m) form the hypothenuse, the even and the odd leg of a primitive Pythagorean triangle (PPT) If we...
  48. F

    PF erased my problem anyways triangle problem

    Homework Statement [PLAIN]http://img832.imageshack.us/img832/5249/unledhbk.png The Attempt at a Solution Alright PF just erased all my work so here is my work without LaTex because I am too frustrated to do this all again Basically I found the vectors QP = <7,8,0> |QP|...
  49. Z

    Moment of inertia of a music triangle

    Moment of inertia of a "music triangle" Homework Statement Find the moment of inertia about an axis thru the centre of mass, perpendicular to the plane of an equilateral triangle consisting of identical rods of length 'l' and mass 'm' connected at their ends. Homework Equations...
  50. L

    Real Analysis problem (easy), Triangle inequality

    Homework Statement > a[1], a[2], a[3], .. , a[n] are arbitrary real numbers, prove that; abs(sum(a[i], i = 1 .. n)) <= sum(abs(a[i]), i = 1 .. n) Homework Equations The Attempt at a Solution I have uploaded my attempt as a pdf file, since I'm not too familiar with the...
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