Erin K.

asked • 10/18/12

(2sin18)(cos18)

Simplify by using the double angle formula.

2 Answers By Expert Tutors

By:

Robert J. answered • 10/19/12

Certified High School AP Calculus and Physics Teacher

Rini C.

Hi Robert,

The question was to simplify 2 sin18cos18  Wouldn't the simplest answer be sin36= sin (2x18)?

Why would I try to use the algorithm above?

Thanks.

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10/20/12

Robert J.

Thanks for your response.

As a high school teacher who answered about 25,000 math problems in the internet, I can't believe that 2 sin 18 cos 18 = sin 36 is all you need to solve. Since 18 degree is a special angle, most likely you are asked to evaluate it. This problem can be found in many precalculus textbooks, such as in the "Avanced Mathematics" by Mr. Brown.

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10/20/12

Arturo O.

sin(2x) = 2 sin(x) cos(x) is an identity, which is true for all x.
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