The line $y = mx$ bisects the angle between the two lines shown below. Find $m$.
The two lines are y = x and y = 2x.
y= x
y =2x
We can find m thusly
m = tan [ (arctan(slope of one line) + arctan(slope of second line) / 2 ]
= tan ([ arctan (2) + arctan(1)] / 2) ≈ 1.387
+1725 
