Question

найдите 3 cos a - 4 sin a / 2 sin a - 5 cos a, если tg a = 3

Answer 1

$\frac{3cos a-4sin a}{2sin a-5cos a}=\\\\\frac{3-4\frac{sin a}{cos a}}{2\frac{sin a}{cos a}-5}=\\\\\frac{3-4tg a}{2tg a-5}=\frac{3-4*3}{2*3-5}=\frac{-9}{1}=-9$