Find the measure of angle V in a triangle given the lengths of its sides.
Check the final answer first, then review the worked steps.
Check the final answer first, then review the worked steps.
3. Assign side lengths: In the given triangle $TUV$, we want to find the measure of angle $V$. Let's denote the side opposite angle $V$ as $t$, the side opposite angle $T$ as $u$, and the side opposite angle $U$ as $v$. From the diagram, we have:
- Side $TU$ (opposite $V$) = $t = 5$
- Side $UV$ (opposite $T$) = $u = 8$
- Side $VT$ (opposite $U$) = $v = 11$
5. Substitute the values: Substitute the known side lengths into the formula:
$$\cos(V) = \frac{5^2 + 8^2 - 11^2}{2 \cdot 5 \cdot 8}$$
6. Calculate the terms in the numerator and denominator:
- $5^2 = 25$
- $8^2 = 64$
- $11^2 = 121$
- $2 \cdot 5 \cdot 8 = 80$
7. Substitute the calculated values back into the equation:
$$\cos(V) = \frac{25 + 64 - 121}{80}$$
8. Perform the addition and subtraction in the numerator:
$$25 + 64 = 89$$
$$89 - 121 = -32$$
9. Complete the calculation for cos(V):
$$\cos(V) = \frac{-32}{80}$$
10. Simplify the fraction:
$$\cos(V) = -\frac{32}{80} = -\frac{2 \cdot 16}{5 \cdot 16} = -\frac{2}{5} = -0.4$$
11. Find the angle V by taking the inverse cosine (arccos):
$$m\angle V = \arccos(-0.4)$$
12. Calculate the value of the angle: Using a calculator, find the arccosine of -0.4.
$$m\angle V \approx 113.578178^\circ$$
13. Round the answer to the nearest tenth: The problem asks for the answer as an integer or a decimal rounded to the nearest tenth.
$$m\angle V \approx 113.6^\circ$$