Question

cos(A + B) . cos ( A - B) = ? ​

Answer 1

Answer:

cos^2A-sin^2b.......

Answer 2

Answer:

cos(A+B)+cos(A−B)

As we know;

(Cos(A+B)=cosAcosB-sinAsinB

Cos(A-B)=cosAcosB+sinAsinB)

(cosAcosB−sinAsinB)+(cosAcosB+sinAsinB)

CosAcosB-sinAsinB+cosAcosB+sinAsinB

CosAcosB+cosAcosB-sinAsinB+sinAsinB

CosAcosB+cosAcosB+0

2cosAcosB

cos(A+B)+cos(A−B) =2cosAcosB

Step-by-step explanation:

2 cosA sinB = sin(A + B) − sin(A − B) 2 cosA cosB = cos(A + B) + cos(A − B) 2 sinA sinB = cos(A − B) − cos(A + B)