Plot Sin (x) for - π or negative x-axis

[stevengj]

@Freya_the_Goddess

how about if the function is

f(x) = sin(x)^(2/5)

You could use

# return the real x^p (if it exists)
realpow(x::Real, p::Rational) =
    isodd(p.den) || x ≥ 0 ? copysign(abs(x)^(1//p.den), x)^p.num : throw(DomainError())

and then call realpow(sin(x), 2//5).

(In general, most math libraries in any language tend not to provide this kind of function, as far as I can tell, because it is a nonstandard branch cut for the x^(1/n) power.)