jika A sudut di kuadran II dan B sudut di kuadran III,sin A=8/10 dan cos B=8/17 tentukan a.sin(A+B) b.cos (A-B) c.tan (A+B)

Teorema phytagoras
a²=10²-8²
a²=36
a=6
Sin A=8/10
Cos A=-6/10
Cos B=-8/17 (nilai cos di kuadran III -)
b²=17²-8²
b²=225
b=15
Sin B=-15/17
Sin (A+B) =sin A cos B + cos A sin B
=8/10.(-8/17) + (-6/10). (-15/17)
=-64/170 + 90/170
=26/170=13/85
Cos (A+B) =cos A cos B - Sin A sin B
=(-6/10). (-8/17) - 8/10.(-15/17)
=48/170 + 120/170
=168/170=84/85
Tan (A+B) =tan A + tan B / 1-tan A.tan B
=-8/6 + 15/8 : 1-(-8/6).15/8
=-32+45/24 : 1+120/48
=13/24 x 48/168
=13/84