## anonymous one year ago If sin theta=3/5 and theta is in quad 2 the exact form of cos (2theta) is Is this even right?

1. anonymous

cos(2θ) = 1 - 2sin^2θ = 1 - 2(3/5)^2 = 7/25

2. anonymous

You need to use the double Angle formula of cos. Since we know sin = 3/5 it makes it a little easier for us. Use $$\huge cos(2\theta ) = 1-2\sin^2\theta =$$ $$\huge 1-2(\frac{9}{25}) =$$ $$\huge \frac{7}{25}$$

3. anonymous

So I concur with you.