Subject: trig functions

Name: melissa
Who is asking: Student
Level: Secondary

Find all solutions in the interval (0,2pi)

I think i should graph it but can't figure out how to enter cos2x into my calculator. Also, can this be used with the quadratic formula? i have no clue what I'm doing.

Hi Melissa,

For either the graphic solution or the algebraic solution it is important to realize that cos2x = (cos x)(cos x) = (cos x)2.

To enter cos2x into your calculator, calculate cos x and square it. For an algebraic solution write y = cos x and then the equation becomes 2 y2 - 3 y - 4 = 0.

Paul and Harley
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