The tangent of angle between the lines whose intercepts on the axes are 4,−5 and 5,−4 respectively

Equation of the line having intercepts a,b is xa+yb=1, and its slope is m=−ba Hence the slope of the line which makes intercepts 4,−5 is m1=−(-5)4=54, and the slope of the  line which makes intercepts 5,−4 is m2=−(-4)5=45 If θ be the acute angle between two lines having slopes m1 and m2 then tan⁡θ=m1−m21+m1m2Hence, tanθ=54-451+1=940 Therefore, tan⁡θ=0.23