Question

sin power 4 minus Cos power 4 equals to 1 - 2 cos query
$\sin ^{4}a - \cos^{4}a = 1 - 2 \cos^{2}a$

Answer 1

Ans.

Now,
$sin ^{4} a - cos ^{4} a \\ = (sin ^{2} a + cos ^{2} a)(sin ^{2} a - cos ^{2} a) \\ = 1 \times (1 - cos ^{2} a - cos ^{2} a) \\ = 1 - 2cos ^{2} a$
I hope that this helps you.