Tentukan nilai sin (a+b) dan sin (a+b) bila diketahui sin a = 3/5, sin b = 4/5

Sin a= depan/miring =3/5 (triple pytagoras 3,4,5) jadi sisi samping=4,jadi:
cos a = 4/5

sin b = 4/5 (triple pitagoras ,4,5) panjang sisi samping=3
cos b = 3/5

sin(a+b)= sin a.cos b + cos a.sin b
=(3/5)(3/5)+(4/5)(4/5)
=9/25+16/25
=25/25
=1
sin(a-b)= sin a.cos b – cos a.sin b
=(3/5)(3/5)-(4/5)(4/5)
=9/25-16/25
=-7/25