trigo/

Asked by kanishkaaggarwal | 25th Nov, 2009, 11:36: AM

Expert Answer:

cosA = tanA

cosA = sinA/cosA

cos2A = sinA

1 - sin2A = sinA

sin2A + sinA - 1 = 0

sinA = [-1±(1+4)]/2 = [-1±5]/2

cos2A = 1 -  sin2A = 1 - [-1±5]2/4 = (4-1-5±25)/4 = (-1±5)/2

Regards,

Team,

TopperLearning.

Answered by  | 25th Nov, 2009, 01:59: PM

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