MathDB
Two trains intersect at an angle theta

Source:

May 10, 2012
trigonometry

Problem Statement

Two train lines intersect each other at a junction at an acute angle θ\theta. A train is passing along one of the two lines. When the front of the train is at the junction, the train subtends an angle α\alpha at a station on the other line. It subtends an angle β(<α)\beta (<\alpha) at the same station, when its rear is at the junction. Show that tanθ=2sinαsinβsin(αβ)\tan\theta=\frac{2\sin\alpha\sin\beta}{\sin(\alpha-\beta)}