# Algebra 2

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I meant to type this one:
If the sine of an acute angle is 0.8, what is the sine of twice that angle?
1.60 or .64?

Thanks

• Algebra 2 -

Neither. Sine can never exceed 1.

If the sine is 0.8, the cosine is 0.6.
(Think of a 3,4,5 right triangle, or use cos^2 = 1 - sin^2)

The sine is 2x is 2 sinx cosx.

In this case, that is 2*(3/5)(4/5)= 24/25

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