A vertical pole(AB) 6 feet long casts a shadow(CB) 55 inches long as shown in the attached image. Since the angle of elevation of sun is . We hav to find the value of .
Firstly, we will change the dimensions of pole(in feet) to the dimension of shadow( in inches) . So, that the dimensions of pole and shadow are same.
Since, 1 feet = 12 inches.
6 feet = inches.
Now, let us consider the triangle ABC in the attached image,
The detailed, step by step explanation and application of integral with appropriate substitution to get the expression for the time of extinction is as shown in the attachment.