Question

r) sin² a + 2 cos² a - 1; A) (1-sin α) (1 + sin a); e) (cos a - 1) (1 + cos a).​

Answer 1

Ответ:

r) $cos^{2}\alpha$

A) $cos^{2}\alpha$

e) $-sin^{2}\alpha$

Объяснение:

r) $sin^{2}\alpha + 2cos^{2}\alpha - 1 = 1 - cos^{2}\alpha + 2cos^{2} - 1 = cos^{2}\alpha$

A) $(1 - sin\alpha)(1 + sin\alpha) = 1 - sin^{2}\alpha = cos^{2}\alpha$

e) $(cos\alpha - 1)(1 + cos\alpha) = (cos\alpha - 1)(cos\alpha + 1) = cos^{2} - 1 = -(1 - cos^{2} \alpha) = -sin^{2}\alpha$