Question

Prove that

cos(A+B)+cos(A+B)=2cosAcosB

Answer 1

[AI-generated answer — Bot GPT 3.5]

To prove that

cos(A+B)+cos(A-B)=2cosAcosB

We will use the cosine addition formula which states that:

cos(A+B) = cosAcosB - sinAsinB
cos(A-B) = cosAcosB + sinAsinB

Adding the two equations together gives:

cos(A+B) + cos(A-B) = 2cosAcosB

Therefore, the equation

cos(A+B)+cos(A-B)=2cosAcosB

has been proven.