You are given a triangle ABC, intersected by the secant MN, which is parallel to the base AB of the triangle.
Let’s write a short statement of the condition:
angle CNM = angle A;
BC = 12 cm;
CM = 6 cm;
CN = 4cm.
Find the side length AC -?
So, triangles CMN and ACB are similar triangles, since angle C is the common angle, angle A = angle N (with two parallel and secant).
Triangles are similar in two corners.
From here we write down the ratio of the parties:
BC / CN = AC / CM, therefore:
AC = CM / CN * BC = (6 * 12) / 4 = 18 cm.
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