Question

A solution of the equation cos² x + sin x + 1 = 0, lies in the interval 

A. (- \(\frac{π}4\), \(\frac{π}4\)) 

B. (\(\frac{π}4\), \(\frac{3π}4\)) 

C. (\(\frac{3π}4\), \(\frac{5π}4\)) 

D. (\(\frac{5π}4\), \(\frac{7π}4\))

Answer 1

1 - sin²x + sin x +1 = 0 

sin²x - sin x - 2 = 0 

sin x = - 1 

x = \(\frac{3π}2\)

Option D