Question

(25)^cosx + (52)^cosx = 2

Answer 1

Пусть a = (2/5)^cos x
(5/2)^cosx = (2/5)^-cosx

Тогда уравнение
a + 1/a = 2
a^2 -2a + 1 = 0
откуда a = 1

5/2^cos x = 1
cos x = 0
x = pi/2 + pi*k