st = _sin(angle);
ct = _cos(angle);
Cache the results of trigonometric functions? Angle does not change between samples。
Clarke transform：src\BLDCMotor.cpp Line 546.
Inverse clarke transform：src\common\base_classes\CurrentSense.cpp Line 42.

// function approximating cosine calculation by using fixed size array
// ~55us (float array)
// ~56us (int array)