How to plot y=|sinx||cosx| without the use of a graphing calcuator?

Question

Just substitute known values? Or is there a better way around this?!

Answer 1

Guide:

$$y=|\sin x||\cos x|= \frac12 |\color{blue}{2 \sin x \cos x}|$$

Now, identify a double angle formula to simplify the expression.

Answer 2

You can use a cathode-ray tube oscilloscope and drive the deflection electrodes with a triangular signal horizontally and a sinusoidal one vertically, but the latter should be rectified. The two signals must be synchronous and units understood so that the horizontal period is $\pi$ and vertical range $\frac12$.

The triangular signal can be obtained by integration of a constant tension and reset logics, and the sinusoid by means of an LC oscillator. (I must admit that this is a kind of analogic calculator, though.)