Diketahui segitiga PQR dengan sudut P dan Q lancip,jika tanP 3/4 dan tanQ 1/3,tentukan sin(P+Q)

jawab
p, q lancip
tan p = 3/4 = (y/x)
x= 4, y = 3 , r = 5
sin p = y/r = 3/5
cos p = x/r  = 4/5
tan  q = 1/3 = y/x
x = 3 , y = 1 , r = √10
sin q = y/r = 1/√10 = 1/10 √10
cos q = x/r = 3/√10 = 3/10 √10

sin(p+q) = sin  p cos q +  cos p sin q = (3/5)(3/10 √10) + 4/5(1/10 √10)
sin(p+q) = 9/50 √10 + 4/50 √10 = 13/50 √10