<span>0,37(x + 200) - 0,97x =158
0,37х + 74 - 0,97х = 158
-0,6х + 74 = 158
-0,6х = 158 - 74
-0,6х = 84
х = 84 : (-0,6)
х = -140
</span>
По формуле приведения sin (π/2 + 5x) = cos 5x
√2 · cos 2x · cos 5x - cos 2x = 0
cos 2x · (√2 · cos 5x - 1) = 0
cos 2x = 0 или √2 · cos 5x - 1 = 0
2x = π/2 + πn cos 5x = 1/√2
x = π/4 + πn/2 5x = arccos (1/√2) + 2πk или 5x = - arccos (1/√2) + 2πm
5x = π/4 + 2πk 5x = - π/4 + 2πm
x = π/20 + 2πk/5 x = - π/20 + 2πm/5