Diketahui cos(A+B) =2/5 dan sin A. sinB =1/10. Nilai cos (A - B) adalah

TriGonoMetRi

cos (a + b) = 2/5
cos a cos b - sin a sin b = 2/5
cos a cos b - 1/10 = 4/10
cos a cos b = 4/10 + 1/10 = 5/10

cos (a - b)
= cos a cos b + sin a sin b
= 5/10 + 1/10
= 6/10
= 3/5