Find sin x =1/Rad5 and cos x < 0, find sin(2x)

Question

Double angle identitiesto find he indicated values

Answer 1

sin(2x) = 2sinxcosx

 

You are given sinx.  All you have to do is find cosx using the Pythagorean theorem.

 

cosx = -√(1 - sin²x)

 

 

sin(2x) = -2sinx√(1 - sin²x)