Question

if A= 30° Show that cos 2A = cos ⁴A -sin ⁴ A​

Answer 1

Step-by-step explanation:

given that A=30°

so let solve LHS first:-

cos2A=cos(2×30°)

=cos(60°)=> 1/2

as we know that LHS=1/2

NOW let solve RHS side

cos⁴A-sin⁴A=cos⁴30°-sin⁴30°

=(√3/2)⁴-(1/2)⁴

= 9/16-1/16

= 8/16

RHS =1/2

so both are equal