Question

Найдите cos2a, если sin a=0,2

Answer 1

Объяснение:

cos2a =

$\cos^{2}(a ) - { \sin}^{2} (a)$

$cos^{2}(a ) = 1 - sin^{2}(a )$

$cos(2a) = 1 - 2 \times {sin}^{2} (a)$

cos2a=1-2*0.2*0.2=1-2*0.04=1-0.08=0.92