Geometry

Angles in a triangle add up to 180

Angles in a quadrilateral add up to 360

exterior angle of a triangle = sum of the interior angles of the other angles in a triangle

In Alternate (Z) angles opposite angles are equal

Corresponding (F) angles have the same angles under the top line of the F shape and under the middle line of the F shape

Sum of Interior Angles in an irregular polygon:
(number of sides - 2) x 180

Tangent = a line that touches the edge of a circle
If a tangent and radius meet at the same point then the angle they make is exactly 90

Chord = any line drawn across a circle
No matter where you draw a chord, the line that cuts it exactly in half (90 degrees) will go through the center point of the circle

If a chord is drawn, when two lines draw to the center point of the circle, the angle nearest the center point is exactly double the angle would be if the triangle was made touching the edge of the circle

If two tangents are drawn from any point outside the circle the tangents will eventually touch, and from the middle of the two tangents there will be an equal distance to get back to the center point. draw a line from the center point to the point where the two tangents touch and you have created two congruent triangles