Cos(A+B)+cos(A-B)=2cosA.cosB
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Answer:
2 cosA cosB
Step-by-step explanation:
cos (A+B) = cosA cosB - sinA sinB ------[1]
cos (A-B) = cosA cosB + sinA sinB ------[2]
[1]+[2]
cos (A+B) + cos (A-B) = cosA cosB - sinA sinB + cosA
cosB + sinA sinB ----(cut both
sinA sinB)
= 2 cosA cosB
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