I also always used the perpendicular to x-axis version, but I like this version ...

daef on Oct 6, 2018 | parent | context | favorite | on: Show HN: Trigonoparty – JavaScript trigonometry vi...

I also always used the perpendicular to x-axis version, but I like this version better bcs the tangent tangents in the point of interrest, plus cotangent and tangent are colinear