The document discusses trigonometric ratios in right triangles. It states that if two angles of one right triangle are congruent to two angles of another right triangle, the triangles are similar and their corresponding ratios are equal. It defines the six trigonometric ratios (sine, cosine, tangent, cosecant, secant, and cotangent) in terms of the sides of a right triangle, using both symbols and words. It also introduces the mnemonic SOHCAHTOA to remember the definitions.