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Solve ΔABC using the Law of Sines Part 1

3. A = 110°, a= 14, b= 9

4. B = 110°, c = 13, b = 21

User Freaker
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1 Answer

1 vote

Answer:

3) B = 37.2°, C = 32.8°, c = 8.1

4) A = 34.4°, C = 35.6°, a = 12.6

Explanation:

To solve for the remaining sides and angles of the triangle, given two sides and an adjacent angle, use the Law of Sines formula:


\boxed{\begin{minipage}{7.6 cm}\underline{Law of Sines} \\\\$(a)/(\sin A)=(b)/(\sin B)=(c)/(\sin C)$\\\\\\where:\\ \phantom{ww}$\bullet$ $A, B$ and $C$ are the angles. \\ \phantom{ww}$\bullet$ $a, b$ and $c$ are the sides opposite the angles.\\\end{minipage}}

Question 3

Given values:

  • a = 14
  • b = 9
  • A = 110°

Substitute the given values into the formula and solve for angle B:


\implies (a)/(\sin A)=(b)/(\sin B)


\implies (14)/(\sin 110^(\circ))=(9)/(\sin B)


\implies 14\sin B=9\sin 110^(\circ)


\implies \sin B=(9\sin 110^(\circ))/(14)


\implies B=\sin^(-1)\left((9\sin 110^(\circ))/(14)\right)


\implies B=37.1632517...^(\circ)


\implies B=37.2^(\circ)

As the interior angles of a triangle sum to 180°:


\implies A+B+C=180^(\circ)


\implies C=180^(\circ)-A-B


\implies C=180^(\circ)-110^(\circ)-37.1632517...^(\circ)


\implies C=32.8367482...^(\circ)


\implies C=32.8^(\circ)

Finally, substitute the values of a, A, and C into the Law of Sines formula and solve for side c:


\implies (a)/(\sin A)=(c)/(\sin C)


\implies (14)/(\sin 110^(\circ))=(c)/(\sin 32.8367482...^(\circ))


\implies c=(14\sin 32.8367482...^(\circ))/(\sin 110^(\circ))


\implies c=8.07866414...


\implies c=8.1


\hrulefill

Question 4

Given values:

  • b = 21
  • c = 13
  • B = 110°

Substitute the given values into the formula and solve for angle C:


\implies (b)/(\sin B)=(c)/(\sin C)


\implies (21)/(\sin 110^(\circ))=(13)/(\sin C)


\implies 21 \sin C=13\sin 110^(\circ)


\implies \sin C=(13\sin 110^(\circ))/(21)


\implies C=\sin^(-1)\left((13\sin 110^(\circ))/(21)\right)


\implies C=35.5712205...^(\circ)


\implies C=35.6^(\circ)

As the interior angles of a triangle sum to 180°:


\implies A+B+C=180^(\circ)


\implies A=180^(\circ)-B-C


\implies A=180^(\circ)-110^(\circ)-35.5712205...^(\circ)


\implies A=34.4287794...^(\circ)


\implies A=34.4^(\circ)

Finally, substitute the values of b, B, and A into the Law of Sines formula and solve for side a:


\implies (a)/(\sin A)=(b)/(\sin B)


\implies (a)/(\sin 34.4287794...^(\circ))=(21)/(\sin 110^(\circ))


\implies a=(21\sin 34.4287794...^(\circ))/(\sin 110^(\circ))


\implies a=12.6349923...


\implies a=12.6

NO LINKS!!!! URGENT HELP PLEASE!!!!! Solve ΔABC using the Law of Sines Part 1 3. A-example-1
NO LINKS!!!! URGENT HELP PLEASE!!!!! Solve ΔABC using the Law of Sines Part 1 3. A-example-2
User Kuba Wyrobek
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