get_bb_tt_diagonal: Get the length of the front triangle diagonal
In ghuiber/bicycle: Design a bicycle frame

Description Usage Arguments Value Examples

The front triangle is a misnomer, because it's a quadrilateral made up by the seat tube ST, top tube TT, head tube HT and down tube DT. The diagonal we want is the second one, going from the bottom bracket BB to the point where the top tube meets the head tube.

1	get_bb_tt_diagonal(st_length, tt_length, st_angle, tt_angle)

`st_length`	The length of the seat tube ST in millimeters.
`tt_length`	The length of the top tube TT in millimeters.
`st_angle`	The angle between the seat tube and the horizontal.
`tt_angle`	The angle between the top tube and the horizontal.