How do you solve # sin x = -cos^2x-1# in the interval [0, 2pi]?
1 Answer
Feb 9, 2016
Explanation:
You can use the law
#sin^2 x + cos^2 x = 1 " "<=> " "cos^2 x = 1 - sin^2 x #
If you plug this into your equation, you have
#sin x = - (1 - sin^2 x) - 1#
#sin x = -2 + sin^2 x#
#sin^2 x - sin x - 2 = 0#
Substitute
#u^2 - u - 2 = 0#
This quadratic equation has two solutions:
Resubstitute:
#sin x = 2 " "# or#" " sin x = -1#
Graph of
graph{sin(x) [-1.18, 7.588, -2.09, 2.294]}