In an isosceles triangle ABC, the base of the AC is 12 cm, the length of the lateral

univerkov | August 9, 2021 | education

In an isosceles triangle ABC, the base of the AC is 12 cm, the length of the lateral edge is 3 cm longer than the base. What is the cosine of the angle at the base?

Determine the length of the side. AB = BC = AC + 3 = 12 + 3 = 15 cm.

Let’s build the height BH. Since the ABC triangle is isosceles, the height BH is also the median of the ABC triangle, then AH = CH = AC / 2 = 12/2 = 6 cm, and the ABН triangle is rectangular.

Determine the cosine of the angle BAC.

CosBAH = AH / BA = 6/15 = 2/5 = 0.4.

Answer: The cosine of the angle at the base is 0.4.

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