4cos2x = - √8
cos(3x + 180º) = √3/2
cos2x-sin2xsecx = 1
Thanks in advance.
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What have you tried with these?
Well we're either factoring or using the trig identities (along with addition/half/double angle formulas)
Some identities could be helpful here, but maybe you don't need them at all.
Take #1 for example
Originally Posted by funkyfiasco Well we're either factoring or using the trig identities (along with addition/half/double angle formulas) Okay, so for example what have you done with this one?
Edit: Slow on the guns again!
for 4cos2x = -√8 I got 67.5 degrees and 112.5 degrees.
I'm still trying to find cos(3x + 180 deg) = √3/2 and the other one.
Thanks for your help
Last edited by funkyfiasco; March 20th 2011 at 05:56 PM.
Originally Posted by funkyfiasco
. Use the addition formula
180 is on the unit circle so you can simplify
Last edited by e^(i*pi); March 20th 2011 at 05:53 PM.
Reason: poor latex
Or you can use the fact that ...
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