Geometry Theorems

ASA (angle side angle)

If two triangles have two angles and the side between them that match exactly, then the two triangles are identical twins (congruent).

SAS (side, angle, side)

If two triangles have two sides and the angle between them that match exactly, then the two triangles are identical twins (congruent).

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SSS (side, side, side)

If all three sides of one triangle match the lengths of the three sides of another triangle, the two triangles are identical twins (congruent).

HL (hypotenuse, leg)

If two right triangles have a matching hypotenuse (the long slanted side) and one matching leg (one of the short sides), then the triangles are identical.

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AAS (angle, angle, side)

If two triangles have two angles and a side that is NOT between them that match, the triangles are identical.

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Triangle Sum Theorem (TST)

The three inside angles of any triangle always add up to exactly 180°.

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Exterior Angle Theorem (EAT)

The outside angle of a triangle is equal to the two inside angles across from it added together.

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Remote Angle Theorem (RAT)

The angle on the outside of a triangle is equal to the sum of the two remote (far away) angles on the inside.

CPCFC

(congruence statements, corresponding parts, finding missing values)

CPCTC

(ID 6 pairs of congruence checks, finding missing values)