aussy123
Write the following expression as a function of a positive acute angle.
cos 125



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terenzreignz
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@aussy123
It might help you to know that with your angle in degrees,
\[\large \cos \ \theta = \sin (90^o  \theta) \]

terenzreignz
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So
\[\large \cos(125^o)=\sin(90^o  125^o)=\sin(35^o)\]

aussy123
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why did you use sin

terenzreignz
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It's an identity. It didn't say to use a specific function, it just says use a function.

aussy123
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oh sorry

terenzreignz
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Get it now?

aussy123
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yes a little

aussy123
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the answer is cos55

terenzreignz
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I suppose so. You're right :)
It stems from the fact that
it's equal to sin(35) = sin(35) = cos(90  35)

aussy123
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I tried that way too, but I also did
cos 125 = cos (180  125) =  cos 55

terenzreignz
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Well, as long as your methods are valid, it should be no problem.

aussy123
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Thank you!

terenzreignz
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No problem :)