if sin a/2 + cos a/2 = -1/2, then sin2a equals..........??

Asked by SHIVANI_SOOD | 14th Apr, 2010, 05:25: PM

Expert Answer:

sin a/2 + cos a/2 = -1/2

Square on both sides,

sin2 a/2 + 2sina/2 cosa/2 + cos2 a/2 = 1/4

1 + 2sina/2 cosa/2  = 1/4

1 + sin a  = 1/4

Hence sin a = -3/4

and cos a = (1 - 9/16) =7/4.

sin 2a = sina cosa = (-3/4)(7/4) = -37/16

Regards,

Team,

TopperLearning.

 

 

Answered by  | 15th Apr, 2010, 10:19: AM

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