Answer:

A linear circuit is a circuit whose output is directly proportional to its input. In other words, the output of a linear circuit is a scaled version of its input. When a linear circuit is excited with a sine or cosine wave, the output of the circuit will also be a sine or cosine wave, but with possibly different amplitude and phase.

Sine/Cosine Wave Signal:
A sine or cosine wave is a periodic signal that can be represented by a mathematical function. It is a smooth waveform that oscillates between positive and negative values. The waveform of a sine or cosine wave is not affected by a linear circuit. The linear circuit can amplify or attenuate the signal, but it does not change the shape or frequency of the waveform.

Effect of Linear Circuit on Other Waveforms:
- Triangular Waveform Signal: A triangular waveform is a periodic signal that ramps up and down in a linear fashion. When a triangular waveform is passed through a linear circuit, the circuit will distort the waveform. The output waveform may have rounded corners and uneven slopes due to the non-linear characteristics of the circuit.
- Rectangular Waveform Signal: A rectangular waveform is a periodic signal that alternates between two levels, typically high and low. When a rectangular waveform is passed through a linear circuit, the circuit will round off the corners of the waveform and introduce overshoot and undershoot. The output waveform may have a slower rise and fall time compared to the input waveform.
- Sawtooth Waveform Signal: A sawtooth waveform is a periodic signal that ramps up and then quickly drops back down to its starting level. When a sawtooth waveform is passed through a linear circuit, the circuit will distort the waveform. The output waveform may have rounded corners and uneven slopes due to the non-linear characteristics of the circuit.

Conclusion:
In conclusion, the waveform of a sine or cosine wave is not affected by a linear circuit. This is because a linear circuit only scales the input waveform and does not introduce any distortion or change in shape. On the other hand, triangular, rectangular, and sawtooth waveforms are affected by linear circuits and may be distorted in terms of shape, amplitude, and timing.