sine, triangle and square wave generator?
There is a multitude of single-chip function generator chips.  One of the oldest was the ICL8038 which was soon followed by the XR2206.  I've used both and probably still have one or two units built many years ago using the 8038.  Both of these are still available.

Modern equivalents include the MAX038, AD9835, AD5932

You can also build a fixed-frequency using a quad op-amp.  This is configured in one of several similar configurations: an integrator followed by a Schmitt trigger, or a square-wave oscillator followed by several integrators.

You get a triangle wave if you integrate a square wave.  You get an approximation of a sine wave if you integrate a triangle wave.

Google is your friend.  Simply search out "function generator" or "function generator ic" and learn to your hearts' content.  Then come back and ask questions.