এখানে যে যে সূত্র ব্যাবহার হয়েছে:

1. Brahmagupta theorem : \[ \text{Area}(\triangle) = \sqrt{(s-a)(s-b)(s-c)(s-d)} \] where \( s \) is the semiperimeter of the quadrilateral, calculated as: \[ s = \frac{a + b + c + d}{2} \]

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2. 
   
   \[ Where : x = \angle B \text{ (in radians)} \]

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3. $$ c^2 = a^2 + b^2 - 2ab \cos(\gamma) $$ where: $$ \begin{align*} c & : \text{third side length} \\ a & : \text{first side length} \\ b & : \text{second side length} \\ \gamma & : \text{angle opposite third side} \end{align*} $$

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4. $$ \text{Area}(\triangle) = \frac{1}{2} \cdot a \cdot b \cdot \sin(C) $$ where: $$ \begin{align*} \text{Area}(\triangle) & : \text{Area of the triangle} \\ a & : \text{Length of side } a \\ b & : \text{Length of side } b \\ C & : \text{Angle opposite side } c \end{align*} $$

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5. \[ \text{Area}(\triangle) = \sqrt{s \cdot (s - a) \cdot (s - b) \cdot (s - c)} \] where \(s\) is the semi-perimeter, calculated as: \[ s = \frac{a + b + c}{2} \]