Two sides of the triangle are  m and  m.

In ,

m, m.

Assume the altitude of the triangle as .

Angle between them is increasing at a rate of  rad/s.

Assume the angle between them as .

.

Find the altitude of the triangle.

Consider

Area of the triangle .

.

Substitute and in above expression.

Differentiate on each side with respect to .

Find rate of change of area when the angle between the fixed sides is .

Substitute and in .

Rate at which the area of the triangle increasing is m²/s.

Rate at which the area of the triangle increasing is m²/s.