See the Proof in Explanation.
We use the Formula
Hence, the Proof.
Is it helpful? Enjoy Maths.!
Answering this question requires the use of two important identities:
#sin^2x+cos^2x=1->#Pythagorean Identity #cos2x=cos^2x-sin^2x->#Double angle identity for cosine
Note that subtracting
Now that we have a few identities to work with, we can do some substituting in
We see that the cosines cancel:
This is another form of the Pythagorean Identity
That's exactly what we have in