$A$

$B$

$C$

$a$

$b$

$D$

$b\sin A$

$b\cos A$

$c-b\cos A$

A = (-1.78, -0.52)
B = (7.98, -0.02)
C = (1.2, 3.26)
poly1, c, a, b = Polygon(A, B, C)
d = OrthogonalLine(C, c)
D = Intersect(d, c)
e = Segment(C, D)
f = Segment(A, D)
g = Segment(D, B)