Question

С0s^2 (a- п/4) - С0s^2 (a+ п/4)

Answer 1

(cos(a-π/4)-cos(a+π/4))(cos(a-π/4)+cos(a+π/4))=
=-2sin(-π/4)sina*2cos(-π/4)cosa=2*√2/2sina*2*√2/2cosa=
=2sinacosa=sin2a