sina=3/5
cosa=4/5
tana=3/4
-tanb=tan(a-b-a)
=[tan(a-b)-tana]/[1+tan(a-b)tana]
=(-1/4)/(11/8)
=-11/2
tanb=11/2
tan(2a-b)=tan(a-b+a)
=[tan(a-b)+tana]/[1-tan(a-b)tana]
=(5/4)/(5/8)
=2
sina=3/5
cosa=4/5
tana=3/4
-tanb=tan(a-b-a)
=[tan(a-b)-tana]/[1+tan(a-b)tana]
=(-1/4)/(11/8)
=-11/2
tanb=11/2
tan(2a-b)=tan(a-b+a)
=[tan(a-b)+tana]/[1-tan(a-b)tana]
=(5/4)/(5/8)
=2