$\"\"$ and $\"\"$ are the sides of the triangle and $\"\"$ and $\"\"$ are the respective opposite angles.

Apply law of sines for the above angles : $\"\"$ .

Find an equation for $\"\"$ by using law of sines.

Consider $\"\"$ .

$\"\"$ .

Area of a triangle $\"\"$ .

Substitute $\"\"$ in equation (1).

$\"\"$

Property of angle : $\"\"$ .

$\"\"$

Apply difference rule of a sine function : $\"\"$ .

$\"\"$

Thus, area of a triangle $\"\"$ .