Peaucellier's linkage allows to transform a rotary-motion into a straight-line motion. The invention that appeared in 1864, was important for the development of steam engine.
Circle Theorem 1 - Angle @ centre = 2xangle @ circumference
Velocity field on a rigid lamina
Spherical Right Triangle All
Finding Sides of Right-Angled Triangles
Fermat Point of a Triangle
Post shadow, lamp in front
Solving Calculus Problems with Geogebra