# Planar two-link inverse kinematics
# Scope: Two-link planar elbow-up solution; target within reach.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

linkA = 200 mm
linkB = 150 mm
x = 250 mm
y = 50 mm

cosElbow := (x^2+y^2-linkA^2-linkB^2)/(2*linkA*linkB)
elbow := acos(cosElbow) [rad]
shoulder := atan2(y/linkA,x/linkA)-atan2(linkB*sin(elbow)/linkA,1+linkB*cos(elbow)/linkA) [rad]

check target in reach: abs(cosElbow) <= 1

scenario alternative: linkA = 160 mm