Hi, can someone please solve this step-by-step for me? I really don't get it...

Directions: Use the quadratic formula to solve the equation in the interval [0,2PI). Then use a graphing utility to approximate the angle x.

4cos^2x-4cosx-1=0

thanks.

1 answer

LET Y = COS X

Then you have

4y^2-4y-1=0

Then use the quadratic equation to solve for y. then put for y, the original value...cosx= solution, and solve for x.
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