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Triangle Proportionality Theorem
If a line parallel to one side of a triangle intersects the other two sides of the triangle, then the line divides these two sides proportionally.
If , then .
Example :
Find the value of .
The lines are parallel.
Therefore, by the Triangle Proportionality Theorem,
Substitute the values and solve for .
Cross multiply.
Divide both sides by .
The value of is .