Question

Упростите выражение

(1 - cos^2 (90° - a))/(1 - sin^2 (90° - a))

Answer 1

$\displaystyle\bf\\\frac{1-Cos^{2} (90^\circ-\alpha ) }{1-Sin^{2}(90^\circ-\alpha )} =\frac{1-Sin^{2} \alpha }{1-Cos^{2} \alpha } =\frac{Cos^{2} \alpha }{Sin^{2} \alpha } =Ctg^{2} \alpha$