We got this question the other day and I'm not exactly sure how to do it.
Given A+B+C= pi
Prove:
cos(2A)+cos(2B)+cos(2C)+1 = -4cos(A)cos(B)cos(C)
The hint was to use product formulas.
Can anybody help me with how I would go about doing this?
We got this question the other day and I'm not exactly sure how to do it.
Given A+B+C= pi
Prove:
cos(2A)+cos(2B)+cos(2C)+1 = -4cos(A)cos(B)cos(C)
The hint was to use product formulas.
Can anybody help me with how I would go about doing this?