证明 cos^2(2t)+sin^2(2t)=1

解答

证明

cos^{2} (2 t) + sin^{2} (2 t) = 1

真

求解步骤

cos^{2} (2 t) + sin^{2} (2 t) = 1

使用毕达哥拉斯恒等式:

cos^{2} (x) + sin^{2} (x) = 1

\Rightarrow 真

p ro v e tan (x + \frac{π}{3}) = \frac{tan ( x ) + 3}{1 - 3 tan ( x )}

p ro v e \frac{1 - 2 sin ^{2} ( x )}{1 - sin ^{2} ( x )} = 1 - tan (2 x)

p ro v e sin (x + y) - sin (x - y) = 2 sin (y) cos (x)

p ro v e sin (2 a) = 2 cos (a) sin (a)

p ro v e sin (2 α) = \frac{2 tan ( α )}{1 + tan ^{2} ( α )}