Answer:
An obtuse triangle has two angles 45 and 18. The value of the unknown angle is
![117^(\circ)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/l269jzl7d87y755646fj91m7ee2hr4vmlr.png)
Solution:
Given that two angles of an obtuse triangle is 45 and 18.
Third angle is θ
We are asked to find the value of third unknown angle theta
According to angle sum property of triangle, sum of three angles of triangle is
![180^(\circ)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4kg7ynbcbrrljc92jzl1775p8j8fjsfmhg.png)
This means in our case sum of 45, 18 and θ should be
![180^(\circ)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4kg7ynbcbrrljc92jzl1775p8j8fjsfmhg.png)
![\begin{array}{l}{=>45+18+\theta=180} \\ {=>\theta=180-63=117^(\circ)}\end{array}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3xrslh7r68x71qv7s1iqhar12ug5btqacl.png)
Hence value of unknown third angle of an obtuse triangle is