How do you graph #x^2+y^2=4#?
See the explanantion
This is the equation of a circle with its centre at the origin.
Think of the axis as the sides of a triangle with the Hypotenuse being the line from the centre to the point on the circle.
By using Pythagoras you would end up with the equation given where the 4 is in fact
To obtain the plot points manipulate the equation as below:
Take the square root of both sides
Now write it as
Calculate and plot a series of points using first the positive version of this equation then repeat using the negative side.
You should then get something that looks like:
The axis scale in mine do not exactly match in scale, so the plot looks a little flattened!