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The question involves finding the solution to:

cos x + root (1-0.5sin2x) = 0

I can get the answer; first by taking one term to the other side, squaring, and then factorising.

My answers are:

0,180,45,225

However, the markscheme requir "Checking for spurious answers due to squaring"

Which results in the answers being 180 and 225. Can someone please explain what is meant by this and why, and how one would "check"?

Thanks

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# Spurious solutions

**Physics Forums | Science Articles, Homework Help, Discussion**