Use the Double-Angle Identity to find the exact value for cos 2x , given #sin x= sqrt2/ 4#?
1 Answer
The first step to answering this question is figuring out which Identity to use, taking into account the information we are given in the question.
For
and
As we are looking for
We know three things at this point:
and
We can use the above to find
Use the identity we chose:
Change the notation to make it easier to manipulate:
Substitute
Square both the numerator and denominator of the fraction:
Expand (break the brackets):
Simplify:
Solve: