Can someone help me prove a few identities for pre-calc?

Megumi Tao

New member
Can someone help me prove a few identities for pre-calc?
Thanks in advance!

cos 5? /sin ? - sin 5? /cos ? = cos 6? /sin ? cos ?

sin 2? cot ? = 2 cos^2 ?

cos 4? = cos^4 ? - 6 sin^2 ? cos^2 ? + sin^4 ?
 
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