Question

Find the real zeros of the trigonometric function on the interval 0 ≤ x < 2π

f(x) = 4 cos^2(x) - 3

Answer 1

4cos2(x)−3=0

or
4cos2(x)=3

cos(x)= √3/2

π/6, 5π/6, 7π/6, 11π/6

Answer 2

f(x) = 4 [cos (x)]^2 - 3 = 0

4[cos(x)]^2 = 3

cos(x) = √3 / 2

That happens in the first and fourth quadrants, for the angles 30 degrees and 330 degrees.

Answer: x = 30 degrees and x = 330 degrees