Function point_in_triangle 

pub fn point_in_triangle(
    x1: f64,
    y1: f64,
    x2: f64,
    y2: f64,
    x3: f64,
    y3: f64,
    x: f64,
    y: f64,
) -> bool

Test if point (x, y) is inside triangle (x1,y1), (x2,y2), (x3,y3).