THE FORMULAS
Here are some of the formulas you may find useful on Geometry questions.
Circles
Think CArd! (Circumference, Area, radius, diameter)
If you have one of these, you can always find the other three.
d = 2r C = πd = 2πr A = πr^2
When dealing with the parts of a circle, set up a ratio.
For Coordinate Geometry, be able to recognize the equation of a circle:
(x − h)^2 + (y − k)^2 = r^2
where (h,k) is the center of the circle, and (x,y) is any point on the circle.
Triangles
Area = A = bh
Perimeter: P = sum of the sides
Sum of all angles: 180°
Similar triangles have congruent angles and proportional sides.
Right Triangles
The Triangle rules apply, but there are some special rules for right triangles.
Pythagorean theorem, where a, b, and c are the sides of the triangle, and c is the hypotenuse:
a^2 + b^2 = c^2
SOHCAHTOA (ratios between sides and angles of right triangles)
