Improved taylor approximation

Extended Taylor series to x − x^3/3! + x^5/5! − x^7/7! + x^9/9! − x^11/11! for more accurate approximation and to avoid tiny jumps in edge cases.

Improving function namings

The module now offers following methods:

• sin
• cos
• tan
• pow
• subtract

Backwards compatibility is supplied for:

• sinus
• cosinus
• tangens
• substract