1.cot^2x+sec^2x=tan^2x+csc^2x

2.cos3x=4cos^3x-3cosx

Can someone help guide me towards the answer but not actually give me the full solution to the answer. Thanks

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- September 28th 2008, 01:04 PMjohntuanTrig identities
1.cot^2x+sec^2x=tan^2x+csc^2x

2.cos3x=4cos^3x-3cosx

Can someone help guide me towards the answer but not actually give me the full solution to the answer. Thanks - September 28th 2008, 01:36 PMskeeter
1. use the Pythagorean identities and in that order on the left side.

They might need a slight rearrangement before you use them.

2. use the sum identity plus the fact that .

you'll also need the double angle identity for cosine - September 28th 2008, 01:39 PM11rdc11
K I'm not really sure how to show what I mean without solving it. This a long way but I thought I show you a different way to work the problem.

Another way to see if the RHS is equal to the LHS is

- September 28th 2008, 03:20 PMSoroban
Hello, johntuan!

Quote:

- September 28th 2008, 03:36 PM11rdc11
Another way to do it using skeeter method

which simplfies to