cos θ = 24/25
The angle lies in quadrant 1; 0<θ<90
Find sin2θ
I know you would use either the formula cos^2θ - sin^2θ or 2sinθcosθ
And I know that the answer is 339/625, but I do not know how to get that answer?
Yes, you use one of those but which? One is $\displaystyle sin(2\theta)$ and which is $\displaystyle cos(2\theta)$? (What happens if $\displaystyle \theta= 0$?)
If $\displaystyle cos(\theta)= 24/25$ and $\displaystyle \theta$ is in the first quadrant what is $\displaystyle sin(\theta)$? (You do know that $\displaystyle sin^2(\theta)+ cos^2(\theta)= 1$, don't you?
Let me see ... is your difficulty that you work the problem out, but you get an answer different from 339/625?
If so, maybe you answer is right. I also get something different from 339/625.
Could you show us what you did to find your answer.?
This is the same kind of problem as the last one. Only you say cos(theta) > 0? In quadrant III, cos < 0, or so I believe. Am I wrong? Do you mean that cos(2 theta) > 0?
Oh, I see. You mean that sin(theta) < 0. In quadrant 3 both functions > 0. That means theta > pi, so 2*theta > 2pi, the answer is probably in quadrant 1. You'd expect the sin(2 theta) to be > 0, right?