GEO-09 · Geometry and Trigonometry

Circle equation and center/radius

Circles and trigonometry · Stage 3

01 · Key idea

Compare the equation with (x−h)²+(y−k)²=r².

Useful rule(x−h)²+(y−k)²=r²

Build on: ADM-02

02 · Worked example

What are the center and radius of (x−2)²+(y+3)²=16?

This teaching example is original and is not an official SAT question.

Reasoning

h=2, k=−3, and r=√16=4.

Answer

Center (2, −3); radius 4

03 · Next step

Practice questions remain in English, as on the SAT.

GEO-09 · Circle equation and center/radius