jika diketahui Sin a = 3 per 5 dan cos b = 4 per 5 Tentukan cos A + B jika a dan b sudut lancip

sin a = 3/5
cos a = 4/5
cos b = 4/5
sin a = 3/5
cos (a+b) = cos a cos b - sin a sin b
= (4/5)(4/5) - (3/5)(3/5)
= 16/25 - 9/25
= 7/25