# Drawing phasors using waveform

I have the question "Using the waveform given, draw a phasor for the following point"

So here is the waveform:

Here is the answer to the question, however I am not sure how this is achieved. I have tried to learn about drawing phasors but I still don't understand how this answer is achieved.

## 2 Answers

There are 360 degrees in a circle. There are also $2\pi$ radians in a circle. So pi/2 represents 90 degrees. Because the zero degree reference is a flat line extending from the origin towards the right, 90 degrees is a vertical line pointing upwards.

A phasor representation represents the complete sinusoidal wave shown, not the wave at the point +90 degrees. The phasor representing the waveform you show will most likely be at 0 degrees, but this depends on the convention used.

If you represent the wave as the real part of a complex vector in the x-y plane, then the point at 90 degrees will be x = 0 and y = 2,8 in the example.

See Khan Academy for a good explanation.