# What is the equation for a half a circle?

##### 2 Answers

Apr 8, 2016

In polar co-ordinates, r = a and

#### Explanation:

The polar equation of a full circle, referred to its center as pole, is r = a. The range for

For half circle, the range for

So, the answer is

r = a and

Apr 8, 2016

In rectangular coordinates, the equation of the upper half of a circle can be written:

#y = sqrt(r^2 - (x-h)^2) + k#

#### Explanation:

The equation of a full circle with centre

#(x-h)^2+(y-k)^2 = r^2#

Hence the upper half of a circle can be expressed as:

#y = sqrt(r^2 - (x-h)^2) + k#

where