geometry

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In triangle ABC, D is the midpoint of BC. Given that AB=3cm, AC=5cm and BC=7cm, find AD.

Guest Apr 1, 2022

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Best Answer

+23246

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I will assume that you can use the Law of Cosines: c² = a² + b² - 2·a·b·cos(C).

1) Find the size of angle(B) in triangle(ABC): b² = a² + c² - 2·a·c·cos(B).

5² = 7² + 3² - 2·7·3·cos(B)

You now know the size of angle(B)

2) Find the length of side AD in triangle(ABD):

AD² = 3² + 3.5² - 2·3·3.5·cos(B)

geno3141 Apr 1, 2022

1⁺⁰ Answers

+23246

+1

Best Answer

I will assume that you can use the Law of Cosines: c² = a² + b² - 2·a·b·cos(C).

1) Find the size of angle(B) in triangle(ABC): b² = a² + c² - 2·a·c·cos(B).

5² = 7² + 3² - 2·7·3·cos(B)

You now know the size of angle(B)

2) Find the length of side AD in triangle(ABD):

AD² = 3² + 3.5² - 2·3·3.5·cos(B)

geno3141 Apr 1, 2022

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