A. Understand similarity in terms of similarity transformations.

1. Verify experimentally the properties of dilations given by a center and a scale factor:

a. A dilation takes a line not passing through the center of the dilation to a parallel line, and leaves a line passing through the center unchanged.

b. The dilation of a line segment is longer or shorter in the ratio given by the scale factor.

https://www.khanacademy.org/math/basic-geo/basic-geo-transformations-congruence/congruent-similar/v/testing-similarity-through-transformations

B. Prove theorems involving similarity.

4. Prove theorems about triangles. Theorems include: a line parallel to one side of a triangle divides the other two proportionally, and conversely; the Pythagorean Theorem proved using triangle similarity.

https://www.khanacademy.org/math/basic-geo/basic-geometry-pythagorean-theorem/basic-geometry-pythagorean-proofs/v/pythagorean-theorem-proof-using-similarity

C. Define trigonometric ratios and solve problems involving right triangles.

6. Understand that by similarity, side ratios in right triangles are properties of the angles in the triangle, leading to definitions of trigonometric ratios for acute angles.

7. Explain and use the relationship between the sine and cosine of complementary angles.

8. Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems.★

https://www.khanacademy.org/math/geometry-home/right-triangles-topic

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