if sin 70=t write the following in terms of t:
1] cos 160
2] cos 70
3] sin 140
you need to use the expansion method right?
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For #1, use the identity .
For #2, use the Pythagorean identity .
For #3, use the double-angle identity .
In all three cases, substitute 70° for x.
Last edited by yeongil; Jul 20th 2009 at 08:35 AM.
could you give me an example for one of them?
Last edited by yeongil; Jul 20th 2009 at 08:37 AM.
wow i don't know why i confused myself with this stuff. Thanks alot i understand now
EDIT: I am sleep deprived. Sigh.
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