cos2x=(1-cosx)/2
Odpovědi
Diskuze
2cos^2(x) - 2sin^2(x) = 1 - cos(x)
2cos^2(x) - 2sin^2(x) + cos(x) - 1 = 0
2cos^2(x) - 2(1-cos^2(x) + cos(x) - 1 = 0
2cos^2(x) - 2 + 2cos^2(x) + cos(x) - 1 = 0
4cos^2(x) + cos(x) - 3 = 0
s: cos(x) = a
4a^2 + a - 3 = 0
a_(1,2) = (-1 ±√(1+48))/8 = (-1 ± 7)/8
a_1 = 6/8 = 3/4 => cos(x) = 3/4 => x = cca 41°25'+2kπ
a_2 = -1 => cos(x) = -1 => x = 2π + 2kπ