Question

已知a,b为锐角,cosa=3/5,tan(a-b)=-1,求cosb+tana的值

Answer 1

a,b为锐角,cosa=3/5,

sina=4/5

tana=4/3

tan(a-b)

=(tana-tanb)/(1+tanatanb)

=(4/3-tanb)/(1+4tanb/3)

(4/3-tanb)/(1+4tanb/3)=-1

4/3-tanb=-1-4tanb/3

-tanb/3=7/3

tanb=-7/3