How to solve this question?

[raymond]

 

[topsquark]

A starting point:
$$sin(2 \theta ) = 2~sin( \theta )~cos( \theta )$$
How do you find $$sin( \theta )$$ and $$cos( \theta )$$?

-Dan

 

[Steven G]

It happens to me all the times when I send an email without the attachment I meant to include.
You forgot to upload the work you have done on this problem.
When you get a chance can you please do so

 

[bZNyQ7C2]

Isn't there an identity about $\displaystyle \sin \left( {\theta + {\textstyle{\pi \over 2}}} \right)$?
Or maybe $\displaystyle \sin \left( {\theta - {\textstyle{\pi \over 2}}} \right)$?

 

[Romsek]

$\displaystyle \sin\left(\theta \pm \dfrac \pi 2\right) = \pm \cos(\theta)$

 

[bZNyQ7C2]

Thanks. I was looking at the diagram, and thinking that might help.

 

[Dr.Peterson]

I would just directly use the definition of the trig functions based on a point on the terminal ray. There is no need to use such an identity here to find [MATH]sin\theta[/MATH] and [MATH]cos\theta[/MATH]. The important part of the problem, of course, is the identity for [MATH]\sin(2\theta)[/MATH].