Question

решить уравнение 3 cos^2-7cosx+4=0

Answer 1

Получится вот так :)

Answer 2

$3cos^{2} x-7cosx+4=0\\cosx=t \\ -1 \leq t \leq 1\\3t ^{2} -7t+4=0\\D=49-48=1\\ \sqrt{D} =1\\t _{1} = \frac{7+1}{6} = \frac{8}{6} \\ \\t_{2} = \frac{7-1}{6} = \frac{6}{6} = 1 \\ \\ cosx=1\\x= \frac{ \pi }{2} + \pi n$