How do you solve #cos(2theta)+cos(theta)=0#?
1 Answer
Jun 8, 2015
Use trig identity:
Call cos x = t, solve the quadratic equation: y = 2t^2 + t - 1 = 0
Since a - b + c = 0, use shortcut. One real root is t = -1 and the other is
a. cos x = t = -1 -->
b.