Question
Find the principal solutions of the equation cos x = 1/2.
A. π/3, 2π/3
B. 2π/3, 5π/3
C. π/3, 5π/3
D. π/6, 5π/6
Answer: C
Solution:
Since cos x is positive in 1st and 4th quadrant, so there are two principal solutions to above equation i.e. x = π/3, 2π-π/3.
So, x = π/3, 5π/3.
