Math Is Fun Forum

bart

Member

Registered: 2010-07-22

Posts: 2

Composite argument property -- please help!

***SOLVED***

I have two more questions about this section that are a little shady -

>>>>"Suppose that cos A = 0.6 and sin A = 0.8.  Suppose that cos B = 0.96 and sin B = 0.28.  Use the composite argument property to find cos (A + B)."

I responded with
cos (A − B) = cos A cos B + sin A sin B
cos(A-B)=0.6*0.96+0.8*0.28
cps(A-B)=0.576+0.224
cos(A+B)=0.129024

arccos0.129024=A+B
A+B=1.441411637

...I'm pretty sure this is correct, but a double check would be greatly appreciated ... so far so good, until-

>>>>"Show that cos -10.6 and sin-10.8 give the same degree measure for angle A."

How am I suppose to use the "composite argument property" to answer this question? (If I'm suppose to use it, it does not say so but it is in the same section...) All I did was punch both of these in my calculator to prove that they have the same degree measure. Surely I cannot put this as an answer, my instructor will think I'm being a smart ---. Here's another just like it-

>>>>"Show that both cos-1 0.96 and sin -1 0.28 give the same degree measure for angle B."

Any geniuses out there willing to help would be greatly appreciated :D

Last edited by bart (2010-07-22 15:20:37)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Composite argument property -- please help!

Hi bart;

Please see my comments over here.

http://www.mathisfunforum.com/viewtopic … 16#p147016

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.