Prove theorems using similarity

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Lesson Plan →Objectives, pacing and practice, built from this lesson's brief.
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HSG.SRT.B.4

**HSG.SRT.B.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.

HSG.SRT.B.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.

What you'll learn

State and prove the Side-Splitter Theorem: a line parallel to one side of a triangle divides the other two sides proportionally
State and prove the converse of the Side-Splitter Theorem
Recognize when to apply the Side-Splitter Theorem in geometric problems
Prove the Pythagorean Theorem using similar right triangles (altitude to hypotenuse method)
Explain how similarity provides an alternative proof strategy for geometric theorems
Apply these theorems to solve problems involving triangles and parallel lines

Review first:

Establish AA similarity criterion

Slides

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Theorems using similarity

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Practice

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Exercise

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