prove sin^4 theta - cos^4 theta = 2sin ^2 theta - 1
Answer:
sin^4 theta - cos^4 theta = (sin^2 theta + cos^2 theta)x
(sin^2 theta - cos^2 theta)
(difference of two squares)
= (1)(sin^2 theta - cos^2 theta)
= sin^2 theta - cos^2 theta
= sin^2 theta - (1 - sin^2 theta)
= 2sin^2 theta - 1 as required
Good Luck!
hollownomore.
