In questions \(1-10\) solve \(\triangle \mathrm{ABC}\) given \(\mathrm{AB}=80 \mathrm{~cm}, \mathrm{BC}=70 \mathrm{~cm}, \mathrm{AC}=62 \mathrm{~cm}\)

Short Answer

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Question: Given a triangle with side lengths a = 80 cm, b = 70 cm, and c = 62 cm, find all angles of the triangle. Answer: To find all the angles in the given triangle, follow the steps outlined in the solution. First, use the Law of Cosines to find angle C. Next, use the Law of Sines to find angle B. Finally, use the fact that the sum of angles in a triangle is 180 degrees to find angle A.

Step by step solution

01

Calculate angle C using the Law of Cosines

The Law of Cosines states that for any triangle with sides a, b, and c, and angle C opposite side c, we have: \[c^2 = a^2 + b^2 - 2 \cdot a \cdot b \cdot cos(C)\] We can plug in the given values for a, b, and c, i.e., a = 80 cm, b = 70 cm, and c = 62 cm, and then solve for angle C: \[62^2 = 80^2 + 70^2 - 2 \cdot 80 \cdot 70 \cdot cos(C)\] Now, we can solve for cos(C): \[cos(C) = \frac{80^2 + 70^2 - 62^2}{2 \cdot 80 \cdot 70}\]
02

Find the angle C

Now compute the value of cos(C) and use inverse cosine to find the angle C: \[C = cos^{-1}\left(\frac{80^2 + 70^2 - 62^2}{2 \cdot 80 \cdot 70}\right)\]
03

Find angle B using the Law of Sines

The Law of Sines states that for any triangle with sides a, b, and c, and angles A, B and C, we have: \[\frac{a}{sin(A)} = \frac{b}{sin(B)} = \frac{c}{sin(C)}\] We can use this relationship to find angle B: \[\frac{70}{sin(B)} = \frac{62}{sin(C)}\] Now, solve for sin(B): \[sin(B) = \frac{70 \cdot sin(C)}{62}\]
04

Calculate angle B

Compute the value of sin(B) and use inverse sine to find the angle B: \[B = sin^{-1}\left(\frac{70 \cdot sin(C)}{62}\right)\]
05

Calculate angle A

Finally, we can compute angle A using the fact that the sum of angles in a triangle is always 180 degrees: \[A = 180 - B - C\] Now we have calculated all three angles of triangle ABC, and the triangle is solved.

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