Draw a function image：

y=ln((x-1)/(x+2))

Draw a function image：

y=abs(sin(3.1415*x)+1)
y=abs((sin(x*3.1415)+1))*0.5

Draw a function image：

y=sinx/(x^3+3x)

Draw a function image：

y=sin3/2x
y=sin1/2x

Draw a function image：

y=sinx+sin2x+sin3x+sin4x+sin5x+sin6x+sin7x+sin8x+sin9x+sin10x+sin11x+sin12x+sin13x+sin14x+sin15x+sin16x+sin17x+sin18x