Diketahui tan A = 3/4, tan B = 7/24, sudut A dan B lancip. cos(A-B)

cos(A-B) = cosAcosB - sin AsinB
= 4/5.24/25+3/5.7/25
=117/125
=117/5

bawa ke segitiga siku siku utk tentukan cos dan sinnya

tan = y/x
tan A= 3/4= y/x
r=√y²+x²
r=√9+16=√25=5
sinA=3/5
cosA=4/5
tan B= 7/24= y/x
r=√y²+x²
r=√49+576=√625=25
sinB=7/25
cosB=24/25
cos(A-B)=cosA.cosB+sinA.sinB
cos(A-B)=4/5.24/25+3/5.7/25
cos(A-B)=96/125+21/125
cos(A-B)=117/125