Answer:
x = 90°
Step-by-step explanation:
Using the identity
cos²x = 1 - sin²x
Given
cos²x - sin x + 1 = 0
1 - sin²x - sin x + 1 = 0
- sin²x - sin x + 2 = 0 ← quadratic equation in sin x ( multiply through by - 1 )
sin²x + sin x - 2 = 0 ← in standard form
(sinx + 2)(sinx - 1) = 0 ← in factored form
Equate each factor to zero and solve for x
sinx + 2 = 0 ⇒ sinx = - 2 ← has no solution as - 1 ≤ x ≤ 1
sinx - 1 = 0 ⇒ sinx = 1 ⇒ x = 90°
solution is x = 90°
