# Is the amplitude of a sine wave increasing or decreasing in this phase?

I'm new to electrical signal, sorry if my question sounds dumb.

Below is a picture from my text book:

It says a sine wave with a phase of 0° starts at time 0 with a zero amplitude. The amplitude is increasing.

I am little bit confused here, shouldn't that be decreasing? If you watch this simulation (choose oscillate) below:

The single point at time 0 is decreasing.

Is my understanding of how waves propagate incorrect or is the textbook wrong?

• use a pencil and paper to draw the wave, from left to right ... ask yourself the same question as you are drawing ... the drawing action is a simulation of the electrical signal Commented May 8, 2020 at 15:47
• The wording in the book is not great, it can confuse. First it says all three waveforms have the same amplitude, which is right, i.e. A*sin(wt). Then below the picture it says that the amplitude is rising, which obviously means only the instantaneous amplitude of the waveform. Anyway, if it is going to more positive direction when time is increasing, it is rising. Commented May 8, 2020 at 16:21