Posted by jeff on Friday, May 28, 2010 at 9:23am.
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  drwls, Friday, May 28, 2010 at 11:15am
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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