Problem

Use the Sine Law in an Ambiguous Case In $\triangle \mathrm{ABC}, \angle \mathrm{A}=30^{\circ}, a=24 \mathrm{~cm}$, and $b=42 \mathrm{~cm}$. Determine the measures of the other side and angles. Round your answers to the nearest unit.

Solution

Step 1 :\(\sin A = \frac{1}{2}\)

Step 2 :\(\frac{a}{\sin A} = \frac{b}{\sin B}\)

Step 3 :\(\frac{24}{\frac{1}{2}} = \frac{42}{\sin B}\)

Step 4 :\(\sin B = \frac{42}{48} = \frac{7}{8}\)

Step 5 :\(B = \sin^{-1} \frac{7}{8}\)

Step 6 :\(B \approx 61^\circ\)

Step 7 :\(C = 180^\circ - A - B \approx 180^\circ - 30^\circ - 61^\circ \approx 89^\circ\)

Step 8 :\(\frac{c}{\sin C} = \frac{a}{\sin A}\)

Step 9 :\(\frac{c}{\sin 89^\circ} = \frac{24}{\frac{1}{2}}\)

Step 10 :\(c \approx 48\)

Step 11 :\(\boxed{A \approx 30^\circ, B \approx 61^\circ, C \approx 89^\circ, a = 24, b = 42, c \approx 48}\)

From Solvely APP
Source: https://solvelyapp.com/problems/15501/

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