Question

Знайти Cos2a якщо Sina=$frac{1}{4}$

Answer 1

cos2a = (1 - 2sin^2a)
sin^2a = 1/4^2 = 1/16
1 - 2*1/16 = 1 - 1/8 = 7/8 =>
cos2a = 0,875

Answer 2

Ответ:

Объяснение:

$sina=frac{1}{4};\sin^2a+cos^2a=1;cos^2a=1-sin^2a=1-(frac{1}{4})^2=1-frac{1}{16}=frac{15}{16};\cos2a=cos^2a-sin^2a=frac{15}{16}-frac{1}{16}=frac{14}{16}=frac{7}{8}$