for angles greater than right angles

Asked by  | 22nd Mar, 2012, 10:05: AM

Expert Answer:

Let x = 120 , y = 150 ,
Now , sin120 = sin(180-60) = sin60 = root3 / 2
Similarly , sin150 = sin30 = 1/2
cos120 = cos(180-60) = -cos60 = -1/2
cos150 = -cos30 = -root3 / 2
 
So L.H.S becomes root3 / 2 * -root3 / 2 + 1/2 * -1/2 = -1
Similarly R.H.S. = sin(120+150) = sin270 = -1
This implies that the for all angles the condition holds.

Answered by  | 22nd Mar, 2012, 03:23: PM

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