Answer:
1 = (sin^2 A + cos^2 A)^2 = sin^4 A + cos^4 A + 2 sin^2 A cos^2 A
so
sin^4 A + cos^4 A
= 1 - 1/2 sin^2 2A
= 1 - 1/4 (1- cos 4A)
= 1/4 (3+cos 4A)
Step-by-step explanation:
hope I helped
