Question

Упростите выражение а)cos²α-1
б)tgα÷ctgα×(1-sin²α)
Решите плиз

Answer 1

$cos^2\alpha  - 1 = cos^2\alpha - (sin^2\alpha + cos^2\alpha ) = - sin^2\alpha</p><p>[tex]\frac{tg\alpha}{ctg\alpha}*(1 - sin^2\alpha) = tg\alpha*\frac{1}{tg\alpha} * cos^2\alpha = cos^2\alpha$