Triangle proportionality (side splitter)HSG.SRT.B.4A line parallel to one side of a triangle divides the other two sides proportionally; use it to find missing segments and the parallel segment.Triangle congruence (SSS, SAS, ASA, AAS, HL)HSG.SRT.B.5Match given pairs of equal sides and angles to the SSS, SAS, ASA, AAS and HL congruence rules, and spot SSA and AAA, which prove nothing.Similar triangles and scale factorsHSG.SRT.B.5Use the scale factor between similar triangles to find a missing side, and the square of the scale factor to compare areas.Special right triangles (45-45-90 and 30-60-90)HSG.SRT.C.6Find missing sides of 45-45-90 and 30-60-90 triangles exactly, using the side ratios 1 : 1 : √2 and 1 : √3 : 2.Trigonometric ratios (sine, cosine, tangent)HSG.SRT.C.6Write the sine, cosine and tangent of an acute angle in a right triangle as fractions, including when one side must first be found.Solving right triangles with trigonometryHSG.SRT.C.8Use sine, cosine and tangent to find a missing side of a right triangle, and inverse trigonometry to find a missing angle.Law of sines and law of cosinesHSG.SRT.D.11Find missing sides and angles of any triangle with the law of sines and the law of cosines.