### 5.21.13 Transform complex exponentials into sin and cos : sincos exp2trig

sincos or exp2trig takes as argument an expression containing complex exponentials.
sincos or exp2trig rewrites this expression in terms of sin and cos.
Input :

sincos(exp(i*x))

Output :

cos(x)+(i)*sin(x)

Input :

exp2trig(exp(-i*x))

Output :

cos(x)+(i)*(-(sin(x)))

Input :

simplify(sincos(((i)*(exp((i)*x))`^`2-i)/(2*exp((i)*x))))

or :

simplify(exp2trig(((i)*(exp((i)*x))`^`2-i)/(2*exp((i)*x))))

Output :

-sin(x)