120 likes | 250 Views
Geometry Mrs. Blanco. 8.4 Similar Triangles. Objectives. Identify similar triangles Use similar triangles in real-life problems. Ex. 1: Writing Proportionality Statements. In the diagram, ∆BTW ~ ∆ ETC a) Write the statement of proportionality . b) Find m TEC . mTEC = 79 °
E N D
Geometry Mrs. Blanco 8.4 Similar Triangles
Objectives • Identify similar triangles • Use similar triangles in real-life problems
Ex. 1: Writing Proportionality Statements In the diagram, ∆BTW ~ ∆ETC a) Write the statement of proportionality. b) Find mTEC. mTEC = 79° c) Find ET and BE NEXT SLIDE 34° 79°
Ex. 1: Writing Proportionality Statements • In the diagram, ∆BTW ~ ∆ETC. • Find ET and BE. 34° CE ET Write proportion. = WB BT 3 ET Substitute values. = 12 20 3(20) = 12ET Cross Multiply 79° 5 = ET Divide So, ET is 5 units and BE is 15 units.
There are three different ways to prove that two triangles are similar. Use the graphic organizer to take notes.
Postulate 25 Angle-Angle Similarity Postulate • If two angles of one triangle are congruent to the two angles of another triangle, then the two triangles are similar. • If K Y and J X, then ∆JKL ~ ∆XYZ.
Ex. 2: Are the two triangles similar? If so, find x and y x=24 and y=16 Yes, ΔPQR~ΔLMN
Ex. 3: Are the two triangles similar? If so, write the similarity statement.
Ex. 4: Are the two triangles similar? If so, write the similarity statement.
Ex. 5: Using Similar Triangles BX= 0.75 miles CX= 2.25 miles
Practice—page 484 #18-26 evenpage 485 #34-44 evenTake 15 minutes