Trigonometry

The remaining trigonometric simplifications instructions are:

• EXPLN and SINCOS to apply Euler idendities in both directions
• TRIGCOS, TRIGSIN: replace $\sin^2$ [resp. $\cos^2$] by $1-\cos^2$ [resp. $1-\sin^2$]
• TRIG: replace complex logarithms with $\arctan$ functions, then does TRIGCOS or TRIGSIN (according to the last call to one of these functions)
• TAN2SC: replace $\tan$ by $\sin/\cos$
• TAN2SC2: replace $\tan(x)$ by $\sin(2x)/(1+\cos(2x))$ or by $(1-\cos(2x))/\sin(2x)$.
• HALFTAN: replace $\sin(x)$, $\cos(x)$ and $\tan(x)$ in terms of $\tan(x/2)$