Triangle Calculator
Solve triangles step by step
The calculator will try to find all sides and angles of the triangle (right triangle, obtuse, acute, isosceles, equilateral), as well as its perimeter and area, with steps shown.
Your Input
Solve the triangle, if $$$a = 9$$$, $$$b = 9 \sqrt{2}$$$, $$$C = 45^0$$$.
Solution
According to the law of cosines: $$$c^{2} = a^{2} + b^{2} - 2 a b \cos{\left(C \right)}$$$.
In our case, $$$c^{2} = 9^{2} + \left(9 \sqrt{2}\right)^{2} - \left(2\right)\cdot \left(9\right)\cdot \left(9 \sqrt{2}\right)\cdot \left(\cos{\left(45^0 \right)}\right) = 81.$$$
Thus, $$$c = 9$$$.
According to the law of sines: $$$\frac{a}{\sin{\left(A \right)}} = \frac{c}{\sin{\left(C \right)}}$$$.
In our case, $$$\frac{9}{\sin{\left(A \right)}} = \frac{9}{\sin{\left(45^0 \right)}}$$$.
Thus, $$$\sin{\left(A \right)} = \frac{\sqrt{2}}{2}$$$.
There are two possible cases:
$$$A = 45^0$$$
The third angle is $$$B = 180^0 - \left(A + C\right)$$$.
In our case, $$$B = 180^0 - \left(45^0 + 45^0\right) = 90^0$$$.
The area is $$$S = \frac{1}{2} a b \sin{\left(C \right)} = \left(\frac{1}{2}\right)\cdot \left(9\right)\cdot \left(9 \sqrt{2}\right)\cdot \left(\sin{\left(45^0 \right)}\right) = \frac{81}{2}$$$.
The perimeter is $$$P = a + b + c = 9 + 9 \sqrt{2} + 9 = 9 \left(\sqrt{2} + 2\right)$$$.
$$$A = 135^0$$$
The third angle is $$$B = 180^0 - \left(A + C\right)$$$.
In our case, $$$B = 180^0 - \left(135^0 + 45^0\right) = 0^0$$$.
This case is impossible, since the angle is nonpositive.