Thursday, January 10, 2013 A B C D H Y P E. Homework Check.

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Presentation transcript:

Thursday, January 10, 2013 A B C D H Y P E

Homework Check

§7.3 Identifying Similar Triangles The triangles shown are similar. List all pairs of congruent angles and write the statement of proportionality. AnglesStatement of Proportionality

§7.3 Identifying Similar Triangles The triangles shown are similar. List all pairs of congruent angles and write the statement of proportionality. Angles Statement of Proportionality

§7.3 Identifying Similar Triangles The triangles shown are similar. List all pairs of congruent angles and write the statement of proportionality. Angles Statement of Proportionality

Postulate: Angle-Angle (AA) Similarity Postulate If two angles of one triangle are congruent to two angles of another triangle, then the two triangles are similar. A B C D E F

Example. Decide whether the triangles can be proved similar. If they are similar, write a similarity statement. If they are not similar, explain why. Not similar. We are only given an angle (A) and a side of congruence. This is not enough to determine if the triangles are similar.

Example. Decide whether the triangles can be proved similar. If they are similar, write a similarity statement. If they are not similar, explain why. Yes, similar

Example. Decide whether the triangles can be proved similar. If they are similar, write a similarity statement. If they are not similar, explain why. Yes, similar

Example. The triangles are similar. Find the value of the variable. Since they’re similar, they have congruent angles. Since they’re similar, they have proportional sides.

You Try It. The triangles are similar. Find the value of the variables.

Similarity Theorems SSS Similarity Theorem ◦ If the lengths of the corresponding sides of two triangles are proportional, then the triangles are similar. SAS Similarity Theorem ◦ If an angle of one triangle is congruent to an angle of a second triangle and the lengths of the sides including these angles are proportional, then the triangles are similar.

Example. Are the triangles similar? If so, state the similarity and the postulate or theorem that justifies your answer. No angles are marked as being congruent, so that leaves us with only the SSS theorem to check.

Example. Are the triangles similar? If so, state the similarity and the postulate or theorem that justifies your answer.

Example. Use the diagram shown to complete the statements.

Yes, there are 2 proofs on your homework. Remember a few things… ◦T◦T here are often shared pieces when triangles overlap. ◦T◦T ake nothing for granted. State that you have right angles. State that they are then congruent. That’s TWO STATEMENTS.