Trigo

Asked by baidshryans | 29th Jan, 2009, 06:49: PM

Expert Answer:

tan (60 - A) + tan (30 + A) =  (tan 60 - tan A) / (1 + tan 60 tan A )  + ( tan 30 + tan A) / (1 - tan 30 tan A) = 2

===>  3 - tan A ) / ( 1 +   3 tan A)   +  1 +   3 tan A ) / (  3  - tan A )   = 2   now solving we get A = 15

===> so sin 2A = sin 30 = 1/2   and  2 cos 4A = 2 cos 60 = 1

Answered by  | 29th Jan, 2009, 11:34: PM

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