Question

Доведіть тотожність…

Answer 1

Ответ:

Объяснение:

$\displaystyle\bf\\\frac{1}{1+tg^2\alpha } +\frac{1}{1+ctg^2\alpha } =\\\\\\=\frac{1}{1+\dfrac{sin^2\alpha }{cos^2\alpha } } +\frac{1}{1+\dfrac{cos^2\alpha }{sin^2\alpha } } =\\\\\\=\frac{1}{\dfrac{cos^2\alpha +sin^2\alpha }{cos^2\alpha } } +\frac{1}{\dfrac{sin^2\alpha +cos^2\alpha }{sin^2\alpha } } =\\\\\\=cos^2\alpha +sin^2\alpha =1$

доказано