Hey, I have a few questions I just can't seem to get down, looking for some help here... 1) sin2x = 2csc2x-tanx 1-cos2x 2) cos(x+y)cos(x-y)=(cosx)^2 +(cosy)^2 -1 3) (cosx)^6 + (sinx)^6 = 1-3(sinx)^2 + 3(sinx)^4 Thanks in advance!
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Originally Posted by orca432 Hey, I have a few questions I just can't seem to get down, looking for some help here... 1) sin2x = 2csc2x-tanx 1-cos2x 2) cos(x+y)cos(x-y)=(cosx)^2 +(cosy)^2 -1 3) (cosx)^6 + (sinx)^6 = 1-3(sinx)^2 + 3(sinx)^4 Thanks in advance! You need to show you work too.. (2) multiply and cancel to complete the proof
for (3) since , you can write: convert all cosines into sines and your proof will be complete.
Originally Posted by harish21 for (3) since , you can write: convert all cosines into sines and your proof will be complete. When I converted them, I got , anyone care to help me?
Originally Posted by orca432 When I converted them, I got , anyone care to help me? substitute this in what you had earlier on finish it...
Here's a little more. Now expand this.
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