1. ## Double Angle Formula

Find the exact value of sin2x.

Sinx = (-4/7)

2. Originally Posted by jumpman23
Find the exact value of sin2x.

Sinx = (-4/7)
You should know from class that $\sin(2x)=2\sin(x)\cos(x)$. You already known sin(x). To find cos(x) you can use the info already given to draw a right triangle and solve for the missing leg needed to find cos(x).