Tolong ajarkan saya bagi yang tahu.

Trigonometri

cos A = 5/13
sin A = 12/13
tan A = 12/5
cot A = 5/12

sin B = 4/5
cos B = - 3/5
tan B = -4/3
cot B = - 3/4

a. (tan A - tan B) /(1 + tan A tan B)=
= (12/5 + 4/3) /(1 + 12/5. (-4/3))
= (12/5 + 4/3) /(1 - 48/15) .....(kalikan 15/15)
= (36 + 20)/(15-48)
= (56)/(-33)

b.(cot A + cot B)/(1 - cot A cot B)=
= (5/12 - 3/4) /(1 - (5/12)(-3/4))
= (5/12 - 3/4)/(1 + 15/48) ......kalikan 48/48
= (20-36)/(48 +15)
= - 16/63