Finding Points of Intersection for Trigonometric Functions

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In summary, two trigonometric functions, y = cos 2x and y = 1 + sinx, are given and we are asked to find the x coordinate of point(s) of intersection on the interval [0, 2∏]. The equation $\cos(2x)=1+\sin(x)$ is written and simplified to $2\sin^2(x)+\sin(x)=0$. The solutions for $\sin(x)$ are found to be 0 and -1/2, which correspond to x = 0, 180 degrees, and 210 degrees. The question is then raised if equations can intersect, and the possible solutions for x are listed as 0, π, 7π/6
  • #1
osafi52
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does anybody know how to solve this problem ?Consider two trigonometric functions y = cos 2x and y = 1 + sinx.(a) Write down the equation in x that you would solve to find the x coordinate of point(s) of intersection of those graphs on [0, 2∏].

(b) Solve your equation, and write down the coordinates of the point(s) of intersection .
 
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  • #2
Re: need HELP on this question

osafi52 said:
Consider two trigonometric functions y = cos 2x and y = 1 + sinx.(a) Write down the equation in x that you would solve to find the x coordinate of point(s) of intersection of those graphs on [0, 2∏].

(b) Solve your equation, and write down the coordinates of the point(s) of intersection .

(a) $\cos(2x)=1+\sin(x)$

(b) $\cos(2x)=1-2\sin^2(x)=1+\sin(x)$
$2\sin^2(x)+\sin(x)=0$
$\sin(x)(2\sin(x)+1)=0$

Can you finish?
 
  • #3
thanks so much for the reply it really helped.once i solved the equation i got x=0 and x= 30 .
 
  • #4
osafi52 said:
thanks so much for the reply it really helped.once i solved the equation i got x=0 and x= 30 .

\(\displaystyle \sin(x) = 0\) at \(\displaystyle x = 0^\circ\) and \(\displaystyle x = 180^\circ\) for $0^\circ \le x < 360^\circ$

\(\displaystyle 2\sin(x)+1 = 0 \implies \sin(x) = -\dfrac{1}{2}\) ... you want to try to find the degree solutions for $x$ again?
 
  • #5
Re: need HELP on this question

greg1313 said:
(a) $\cos(2x)=1+\sin(x)$

(b) $\cos(2x)=1-2\sin^2(x)=1+\sin(x)$
$2\sin^2(x)+\sin(x)=0$
$\sin(x)(2\sin(x)+1)=0$

Can you finish?
Hi. thanks for the reply. i solved the equation and got x =0 and x=-30. firstly is this correct and does this answer the question b.
 
  • #6
skeeter said:
\(\displaystyle \sin(x) = 0\) at \(\displaystyle x = 0^\circ\) and \(\displaystyle x = 180^\circ\) for $0^\circ \le x < 360^\circ$

\(\displaystyle 2\sin(x)+1 = 0 \implies \sin(x) = -\dfrac{1}{2}\) ... you want to try to find the degree solutions for $x$ again?

thanks for that. 2sinx+1=0 should have got x=-30.
 
  • #7
osafi52 said:
thanks for that. 2sinx+1=0 should have got x=-30.

how about x = 210 (or -150) ... ?
 
  • #8
Just a thought question: Do "equations" intersect?
 
  • #9
$$x\in\left\{0,\pi,\frac{7\pi}{6},\frac{11\pi}{6},2\pi\right\}$$
 

1. What is the "intersection" of two equations?

The intersection of two equations refers to the point or points where the two lines or curves represented by the equations meet or cross each other.

2. How do you find the intersection of two equations?

To find the intersection of two equations, you can use a variety of methods such as graphing, substitution, or elimination. Graphing involves plotting both equations on the same graph and finding the point where they intersect. Substitution involves solving one equation for a variable and plugging it into the other equation to find the point of intersection. Elimination involves manipulating the equations to eliminate one variable and then solving for the other variable.

3. What does it mean if two equations have no intersection?

If two equations have no intersection, it means the lines or curves represented by the equations do not intersect each other. This could happen if the equations represent parallel lines or if they represent two curves that do not cross each other.

4. Can two equations have more than one intersection?

Yes, two equations can have more than one intersection. This occurs when the equations represent two curves that intersect at more than one point, such as a circle and a line.

5. How can the intersection of two equations be used in real life?

The intersection of two equations has many applications in real life, such as in solving systems of equations to find the optimal solution for a business problem, determining the break-even point for a company, or finding the point of intersection between supply and demand curves in economics. It can also be used in engineering and physics to find the point where two objects or forces intersect.

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