# Homework Help: Find the X and Y point in the graph

1. Jul 2, 2011

### prasantha60

1. The problem statement, all variables and given/known data

In the graph i know the (X,Y) position of the point A , i know the Distance between point A and B , i know the angle also . how can i find the position (X,Y) of point B ?

2. Relevant equations

3. The attempt at a solution

2. Jul 2, 2011

### rock.freak667

Look up how to find the length of a line given two points and how to find the gradient of a line.

(Hint: the gradient of a line is also the same as the tangent of the angle that the lines makes with a horizontal line)

3. Jul 2, 2011

### HallsofIvy

You know what angle? If you know the angle the line through A and B makes with the horizontal (x-axis), which is what rock freak667 assumes, then draw the horizontal at A, the vertial at B and look at the right triangle you have drawn! The x difference between and B is the "near side", the y difference between A and B is the "opposite side", and the straight line from A to B is the "hypotenuse".

4. Jul 2, 2011

### Ashwin_Kumar

Well, it depends alot on the angle. Take the distance between a and b to be 'h' cm and the angle to be 'θ'.
Also note that 'r' cm is negative if B is to the left of A,or below A, and is positive if B is above or to the right of A. Similarly, θ is negative if B is to the left of point A.
The sine of angle θ will tell give you a good idea because since you know the hypotenuse(h cm), you can determine the horizontal difference and then using a cosine(or pythagoras theorem) you can derive at the vertical difference. So, if
$A=[x,y]$

$B=[x+h*sin(θ),y+h*cos(θ)]$

So similarly, to find the value of of 'h' if you know the positions of A and B, use simple inverse trignometry to define 'r'. You can define all unknown values with knowledge of every other value. if you are finding it hard to remember, just draw a right-angle triangle to make sense of it.
Note: Angle θ is obtained by drawing a line parallel to the y axis to the x-axis.
_______________
This will help a lot:
α β γ δ ε θ λ μ ν π ρ σ τ η φ χ ψ ω Γ Δ Θ Λ Π Σ Φ Ψ Ω
∂ ∏ ∑ ← → ↓ ↑ ↔ ⇐⇑⇒⇓⇔
± − ÷ √ ∫ ½ ∞∴ ~ ≈ ≠ ≡ ≤ ≥ ° ∇∝

Last edited: Jul 2, 2011
5. Jul 2, 2011

### Ashwin_Kumar

You aren't replying? So I guess you have managed to solve it.

6. Jul 3, 2011

### eumyang

EDIT: Oops!

Last edited: Jul 3, 2011
7. Jul 3, 2011

### Ashwin_Kumar

Dude. I responded yesterday. And I wrote this today. Look properly.

8. Jul 3, 2011

### Ashwin_Kumar

The posts are over one day apart lol

9. Jul 3, 2011

### SammyS

Staff Emeritus
Hi Ashwin_Kumar ! I see that your relatively new to PF ... Welcome!

Yes !! This sort of thing (the Original Poster not returning or acknowledging answers) happens all too often.

Thanks for helping user prasantha60 and don't let this discourage you. Keep helping where & when you can !!!

SammyS