When two triangles are exactly equal: the SAS, ASA, SSS and RHS rules, the properties of an isosceles triangle, and the inequalities between the sides and angles of a triangle.
3 lessons, about 1 h 35 min3 simulations11 problems6 practice questionsPython in every lesson
Created by StemPy LabTwo figures are congruent when one fits exactly on the other. Congruent triangles have equal corresponding parts, which we shorten to CPCT. The SAS rule says that two sides and the angle between them fix a triangle completely.
Four more rules prove congruence: ASA, AAS, SSS and RHS. ASA is two angles and the side between them, and AAS is two angles and a side elsewhere. SSS is three sides, and RHS is a right angle with the hypotenuse and one side. AAA and SSA do not prove it.
In a triangle with two equal sides, the angles opposite them are equal, and the converse is true. The perpendicular from the apex to the base bisects both the base and the apex angle. A longer side lies opposite a larger angle, and any two sides together are longer than the third.
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