Prove
Cos7a+cosa=2cos4acos3a
Answers
Answered by
1
Answer:
cosx+cosy=2cosx+y/2.cosx-y/2
cos7a+Cosa=2cos((7a+a)/2).cos((7a-a)/2)
=2cos8a/2.cos6a/2
=2cos4acos3a=Rhs
Answered by
3
cos 7a+cosa=2cos4acos3a
cosx+cosy=2cosx+y/2. cosx-y/2. cos7a+Cosa=2cos((7a+a)/2).cos((7a-a)/2) . =2cos8a/2.cos6a/2. =2cos4acos3a=Rhs.
Similar questions