How do you find the solution to csc^2theta-6csctheta+8=0 if 0<=theta<2pi?

1 Answer

theta=pi/6 or theta=5pi/6 or theta=arcsin(1/4) or theta=pi-arcsin(1/4)

Explanation:

You can use the quadratic formula, in the form:

x=-b/2+-sqrt(( b/2)^2-c),

useful when b is even and a=1.

Then

csctheta=3+-sqrt(9-8)

csctheta=2 or csctheta=4

that's

sintheta=1/2 or sintheta=1/4

theta=pi/6 or theta=(5pi)/6 or theta=arcsin(1/4) or theta=pi-arcsin(1/4)