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=−baHence the slope of the line which makes intercepts  4,−5 is m1=−54  , and the slope of the line which makes intercepts 5,−4 is m2=−45 If θ be the acute angle between two lines having slopes m1  and m2 then  tanθ=m1−m21+m1m2Hence, tanθ=−54+451+1=940Therefore, tanθ=0.23