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 Math Central Quandaries & Queries
 Question from Kayla, a student: Find \cos 2 \theta if \sin \theta = \frac{11}{61}.

What is $cos(\theta)?$ Hint: Pythagoras

Do you know a formula for $\cos(2 A)$ in terms of $\sin(A)$ and $\cos(A)?$ (If not, look it up & learn it!)

Good Hunting!

RD

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