We are given a triangle $ABC$ with side $b = 14.35$ cm, side $a = 7.82$ cm, and angle $B = 115^\circ 12'$. We are asked to solve the triangle completely, which means finding the remaining side $c$ and angles $A$ and $C$.

GeometryTriangleLaw of SinesTrigonometryAngle CalculationSide CalculationTriangle Solution
2025/3/13

1. Problem Description

We are given a triangle ABCABC with side b=14.35b = 14.35 cm, side a=7.82a = 7.82 cm, and angle B=11512B = 115^\circ 12'. We are asked to solve the triangle completely, which means finding the remaining side cc and angles AA and CC.

2. Solution Steps

First, convert the angle BB to decimal degrees. Since there are 60 minutes in a degree, 1212' is equal to 1260=0.2\frac{12}{60} = 0.2 degrees. So, B=115.2B = 115.2^\circ.
We can use the Law of Sines to find angle AA:
asinA=bsinB\frac{a}{\sin A} = \frac{b}{\sin B}
sinA=asinBb\sin A = \frac{a \sin B}{b}
sinA=7.82sin115.214.35\sin A = \frac{7.82 \sin 115.2^\circ}{14.35}
sinA=7.82×0.904714.357.07514.350.493\sin A = \frac{7.82 \times 0.9047}{14.35} \approx \frac{7.075}{14.35} \approx 0.493
A=arcsin(0.493)A = \arcsin(0.493)
A29.53A \approx 29.53^\circ
Now, we can find angle CC using the fact that the sum of the angles in a triangle is 180180^\circ:
A+B+C=180A + B + C = 180^\circ
C=180ABC = 180^\circ - A - B
C=18029.53115.2C = 180^\circ - 29.53^\circ - 115.2^\circ
C=35.27C = 35.27^\circ
Finally, we can use the Law of Sines again to find side cc:
csinC=bsinB\frac{c}{\sin C} = \frac{b}{\sin B}
c=bsinCsinBc = \frac{b \sin C}{\sin B}
c=14.35sin35.27sin115.2c = \frac{14.35 \sin 35.27^\circ}{\sin 115.2^\circ}
c=14.35×0.57740.9047c = \frac{14.35 \times 0.5774}{0.9047}
c8.2850.90479.158c \approx \frac{8.285}{0.9047} \approx 9.158 cm

3. Final Answer

A29.53A \approx 29.53^\circ
C35.27C \approx 35.27^\circ
c9.16c \approx 9.16 cm

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