i have no idea how to build a circuit which will indicate if the wave is a sine wave or square wave or triangular wave....i cannot use micro-controllers and oscilloscope....any ideas would be welcome....
Thanks in advance......

 

Sounds like homework. What have you done so far in solving it? What tools do you have to work with? John

edit: Have you read this section? Look about 3/4 the way down.
http://www.allaboutcircuits.com/vol_2/chpt_1/3.html

 

What might be useful is knowing that a sine wave has no harmonics and a triangular wave is composed of the fundamental + odd harmonics.

Have a look at:
http://resonanceswavesandfields.blogspot.com/2009/05/symmetries-in-fourier-series.html

And in particular, this figure:
http://2.bp.blogspot.com/_gQen9AZHznw/SgjFL4NAj4I/AAAAAAAABrI/lWKx96SWE-A/s1600-h/SquareWave250w.gif

Implementation is left as an exercise for the student.

 

An FFT (Fast Fourier Transform) of each equation will let you know the general "shape" it would have on a scope.

--ETA: Hint One method to do it, unsure how complicated your instructor would like though.

Integrate square wave for a triangle wave. Integrate a triangle wave for a sine wave.

Differentiation reverses the process.

 

thanks a lot guys...will definitely try something with these inputs.....