Question

Show that cos4A-Sin4A=1-2Sin2A ​

Answer 1

Answer:

Cos^4A - Sin^4A = 1 - 2Sin^2A

Starting with left side

cos^4-sin^4

=(cos^2+sin^2)(cos^2-sin^2)

=(cos^2+sin^2)(1-sin^2-sin^2)

=1(1-2sin^2)

=1-2sin^2

verified:

left side = right side

Step-by-step explanation: