diketahui tg a=3/4 dan sin b=5/13 dengan sudut a dan b lancip, nilai sin (a+b)=.....

Trigonometri

tan a = 3/4 = y/x
triple x,y,r = 4,3,5
sin a= y/r = 3/5
cos a =x/r =  4/5

sin b = 5/13= y/r
triple x,y,r = 12,5,13
cos b = x/r = 12/13

sin (a+b) = sin a cos b  + cos a sin b
sin (a+b) = (3/5)(12/13) + (4/5)(5/13)
sin(a+b) = (36/65 + 20/65) = 56/65