Question

How do you find the exact value of sin2x using the double angle formula?

Answer 1

The double angle formula says that
`sin(2x) = 2 sin(x) cos(x)`

This is an exact formula, so if you have `sin(x)` and `cos(x)` you can get `sin(2x)`.

If you are given only `cos(x)`, for example, you can use
`sin(x) = pm sqrt(1 - cos^2(x))`
where the quadrant of the angle determines the sign.