Question

Доказать тождество
sin²L · (1+ctg²L) - cos²L = sin²L

Answer 1

$sin^2L*(1+ctg^2L)-cos^2L=\\ \\sin^2L*(1+ \frac{cos^2L}{sin^2L} )-cos^2L=\\ \\ sin^2L+cos^2L-cos^2L=sin^2L$