3. Similar Triangles
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Create a proportion using the properties of similar triangles.
20 in.
Let's begin with recalling that, according to the Angle-Angle Similarity Theorem, if two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar. This means that the drawn triangles are similar.
a/b=.a /d./.b /d.
.a /b./.c /d.=a/b*d/c
Multiply fractions
a/b=.a /3./.b /3.
Cross multiply
Multiply
.LHS /2.=.RHS /2.
Rearrange equation