SOLUTION: For the life of me, I cannot solve 4cos^2x - sinx -5 = 0. Any help would be appreciated.

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Question 167218: For the life of me, I cannot solve 4cos^2x - sinx -5 = 0. Any help would be appreciated.
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
For the life of me, I cannot solve 4cos^2x - sinx -5 = 0. Any help would be appreciated
4COS%5E2x+-+SINx+-5+=+0

Use the Pythagorean identity COS%5E2alpha=1-SIN%5E2alpha
to replace COS%5E2x by 1-SIN%5E2x

4%281-SIN%5E2x%29+-+SINx+-5+=+0

4-4SIN%5E2x+-+SINx+-5+=+0

-4SIN%5E2x+-+SINx+-1+=+0

Multiply thru by -1

4SIN%5E2x+%2B+SINx+%2B1+=+0

This is a quadratic in SINx

But it can have no solution since the discriminant
would be negative  b%5E2-4ac=1%5E2-4%2A4%2A1=1-16=-15

Edwin