tan(a+b)=2/5,tan(a-90)=1/4,tan(b+90)=?

问题描述:

tan(a+b)=2/5,tan(a-90)=1/4,tan(b+90)=?

∵tan(a+b)=2/5,tan(a-90)=1/4,
∴tan(b+90)=tan((a+b)-(a-90))
=(tan(a+b)-tan(a-90))/(1+tan(a+b)*tan(a-90))
=((2/5)-(1/4))/(1+(2/5)*(1/4))
=3/22.