Cosines and SinesDate: 6/16/96 at 14:57:1 From: Anonymous Subject: Cosines and Sines I'd like some information about this sentence because it seems unbelievable to me: cos angle A = sin (90 degrees - angle A) Date: 6/17/96 at 12:4:38 From: Doctor Dave Subject: Re: Cosines and Sines Dear Boschem, Recall that Sin(a+b) = Sin(a)Cos(b) + Cos(a)Sin(b) and Sin(a-b) = Sin(a)Cos(b) - Cos(a)Sin(b) also Sin(90)=1 and Cos(90)=0 so cos(a) = sin(90-a) = sin(90)cos(a) - sin(a)cos(90) = 1cos(a) - 0sin(a) = cos(a) -Doctor Dave, The Math Forum Check out our web site! |
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