Option C:
x = 90°
Solution:
Given equation:
<u>To find the degree:</u>
Subtract 1 + cos²x from both sides.
Using the trigonometric identity:
Let sin x = u
Factor the quadratic equation.
u + 2 = 0, u – 1 = 0
u = –2, u = 1
That is sin x = –2, sin x = 1
sin x can't be smaller than –1 for real solutions. So ignore sin x = –2.
sin x = 1
The value of sin is 1 for 90°.
x = 90°.
Option C is the correct answer.