How do you solve cos(x/2) - sin(x) = 0?

1 Answer
Apr 30, 2016

pi + 2kpi
2kpi
(5pi)/3 + 2kpi

Explanation:

Use trig identity: sin x = 2sin (x/2).cos (x/2). We get:
cos (x/2)- sin (x/2).cos (x/2) = 0
cos (x/2)(1 - 2sin x) = 0
a. cos (x/2) = 0 -->arc x/2 = pi/2 and arc x = (3pi)/2 -->
x = pi and x = 3pi.
General answer -->x = pi + 2kpi
b.sin (x/2) = 1/2.
Trig table and unit circle give:
x/2 = pi/6 and x/2 = (5pi)/6 -->
x = (2pi)/6 and x = (5pi)/3
General answers:
x = pi + 2kpi
x = 2kpi
x = (5pi)/3 + 2kpi