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How do you solve this

How do you solve this-example-1
User John In MD
by
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1 Answer

7 votes

Answer:

Θ ≈ 103°

Explanation:

using the Cosine rule in Δ ABC

cosB =
(a^2+c^2-b^2)/(2ac)

where a is the side opposite ∠ A , b the side opposite ∠ B and c the side opposite ∠ C

here a = 42 , b = 78 and c = 57 , then

cos B =
(42^2+57^2-78^2)/(2(42)(57))

=
(1764+3249-6084)/(4788)

=
(5013-6084)/(4788)

=
(-1071)/(4788) , then

B = Θ =
cos^(-1) ( -
(1071)/(4788) ) ≈ 103° ( to the nearest degree )

User Kareem Kamal
by
8.3k points

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