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Etymology of Cosine

Date: 5/21/96 at 11:4:2
From: Anonymous
Subject: Cosine

I am writing to find out who/where cosine came from. I found out about 
sine from Dr. Math, but I didn't see anything about cosine. Could you 
help me?
					Kenny Allen

Date: 7/2/96 at 22:15:51
From: Doctor Robert
Subject: Re: Cosine

The word cosine is short for "complementary sine".  You will notice 
that the cosine of an acute angle is always equal to the sine of that 
angle's complement.  For example, cos 60 = sin 30, or cos 27 = sin 63. 

-Doctor Robert,  The Math Forum
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Associated Topics:
High School Trigonometry

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