Find cos(A - B) and cos(A) - cos(B) given A+B=60 and CosA + Cos B=1

A+B=60degrees and CosA + Cos B=1 ....find

1) cos(A-B)

2)cosA - Cos B

Re: trignometry --problem plz help

You have: A+B=60° and cos(A)+cos(B)=1

If you write:

cos(A)+cos(B)=1 as 2cos((A+B)/2).cos((A-B)/2)=1

You can solve this one because you know A+B=60° so (A+B)/2=30°

You have now: 2cos(30°).cos((A-B)/2)=1

Now try to finish it.

Re: trignometry --problem plz help

from given cosA = cos(60-B) substituting in 2nd and simplifying

we get cos(B-30) = 1/(sqrt3) gives B = 84.73561

now you can find A and required values