Answer:
![\displaystyle A_{\text{Total}}\approx45.0861\approx45.1](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A_%7B%5Ctext%7BTotal%7D%7D%5Capprox45.0861%5Capprox45.1)
Step-by-step explanation:
We can use the trigonometric formula for the area of a triangle:
![\displaystyle A=\frac{1}{2}ab\sin(C)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B1%7D%7B2%7Dab%5Csin%28C%29)
Where a and b are the side lengths, and C is the angle <em>between</em> the two side lengths.
As demonstrated by the line, ABCD is the sum of the areas of two triangles: a right triangle ABD and a scalene triangle CDB.
We will determine the area of each triangle individually and then sum their values.
Right Triangle ABD:
We can use the above area formula if we know the angle between two sides.
Looking at our triangle, we know that ∠ADB is 55 DB is 10.
So, if we can find AD, we can apply the formula.
Notice that AD is the adjacent side to ∠ADB. Also, DB is the hypotenuse.
Since this is a right triangle, we can utilize the trig ratios.
In this case, we will use cosine. Remember that cosine is the ratio of the adjacent side to the hypotenuse.
Therefore:
![\displaystyle \cos(55)=\frac{AD}{10}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Ccos%2855%29%3D%5Cfrac%7BAD%7D%7B10%7D)
Solve for AD:
![AD=10\cos(55)](https://tex.z-dn.net/?f=AD%3D10%5Ccos%2855%29)
Now, we can use the formula. We have:
![\displaystyle A=\frac{1}{2}ab\sin(C)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B1%7D%7B2%7Dab%5Csin%28C%29)
Substituting AD for a, 10 for b, and 55 for C, we get:
![\displaystyle A=\frac{1}{2}(10\cos(55))(10)\sin(55)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B1%7D%7B2%7D%2810%5Ccos%2855%29%29%2810%29%5Csin%2855%29)
Simplify. Therefore, the area of the right triangle is:
![A=50\cos(55)\sin(55)](https://tex.z-dn.net/?f=A%3D50%5Ccos%2855%29%5Csin%2855%29)
We will not evaluate this, as we do not want inaccuracies in our final answer.
Scalene Triangle CDB:
We will use the same tactic as above.
We see that if we can determine CD, we can use our area formula.
First, we can determine ∠C. Since the interior angles sum to 180 in a triangle, this means that:
![\begin{aligned}m \angle C+44+38&=180 \\m\angle C+82&=180 \\ m\angle C&=98\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7Dm%20%5Cangle%20C%2B44%2B38%26%3D180%20%5C%5Cm%5Cangle%20C%2B82%26%3D180%20%5C%5C%20m%5Cangle%20C%26%3D98%5Cend%7Baligned%7D)
Notice that we know the angle opposite to CD.
And, ∠C is opposite to BD, which measures 10.
Therefore, we can use the Law of Sines to determine CD:
![\displaystyle \frac{\sin(A)}{a}=\frac{\sin(B)}{b}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7B%5Csin%28A%29%7D%7Ba%7D%3D%5Cfrac%7B%5Csin%28B%29%7D%7Bb%7D)
Where A and B are the angles opposite to its respective sides.
So, we can substitute 98 for A, 10 for a, 38 for B, and CD for b. Therefore:
![\displaystyle \frac{\sin(98)}{10}=\frac{\sin(38)}{CD}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7B%5Csin%2898%29%7D%7B10%7D%3D%5Cfrac%7B%5Csin%2838%29%7D%7BCD%7D)
Solve for CD. Cross-multiply:
![CD\sin(98)=10\sin(38)](https://tex.z-dn.net/?f=CD%5Csin%2898%29%3D10%5Csin%2838%29)
Divide both sides by sin(98). Hence:
![\displaystyle CD=\frac{10\sin(38)}{\sin(98)}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20CD%3D%5Cfrac%7B10%5Csin%2838%29%7D%7B%5Csin%2898%29%7D)
Therefore, we can now use our area formula:
![\displaystyle A=\frac{1}{2}ab\sin(C)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B1%7D%7B2%7Dab%5Csin%28C%29)
We will substitute 10 for a, CD for b, and 44 for C. Hence:
![\displaystyle A=\frac{1}{2}(10)(\frac{10\sin(38)}{\sin(98)})\sin(44)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B1%7D%7B2%7D%2810%29%28%5Cfrac%7B10%5Csin%2838%29%7D%7B%5Csin%2898%29%7D%29%5Csin%2844%29)
Simplify. So, the area of the scalene triangle is:
![\displaystyle A=\frac{50\sin(38)\sin(44)}{\sin(98)}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A%3D%5Cfrac%7B50%5Csin%2838%29%5Csin%2844%29%7D%7B%5Csin%2898%29%7D)
Therefore, our total area will be given by:
![\displaystyle A_{\text{Total}}=50\cos(55)\sin(55)+\frac{50\sin(38)\sin(44)}{\sin(98)}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A_%7B%5Ctext%7BTotal%7D%7D%3D50%5Ccos%2855%29%5Csin%2855%29%2B%5Cfrac%7B50%5Csin%2838%29%5Csin%2844%29%7D%7B%5Csin%2898%29%7D)
Approximate. Use a calculator. Thus:
![\displaystyle A_{\text{Total}}\approx45.0861\approx45.1](https://tex.z-dn.net/?f=%5Cdisplaystyle%20A_%7B%5Ctext%7BTotal%7D%7D%5Capprox45.0861%5Capprox45.1)