编写一个函数发生器，要求 :

能够通过用户界面选择产生正弦波、三角波、锯齿波、方波等函数波形

用曲线图控件绘制用户选择的波形。

-Write a function generator requirements:

Can be selected via the user interface to generate sine, triangle, sawtooth, square wave function waveform

Waveforms selected by the user to draw a graph control.