What is the formula for calculating the volume of a pyramid?

4] (a) If the points \( A(1,4), B(-1,-2) \) and \( C(2,-3) \) are vertices atriangle, prove that.. \( \triangle A B C \) is right angled at \( B \), and find its area

ABCD is a trapezoid where \( \overline{\mathrm{AB}} / / \overline{\mathrm{CD}}, \mathrm{A}(9,-2), \mathrm{B}(3,2) \) , \( \mathrm{C}(x,-x) \) and \( \mathrm{D}(4,-3) \) Find the coordinates of the point C

14. Find the radius of a hemisphere of volume \( 80 \mathrm{~cm}^{3} \)

An equilateral triangle it's perimeter equals 27 cm , then it's side length is......

1. \( \triangle A B C \) is right angled at \( A \). \( A D \) is perpendicular to \( B C \). If \( A B=8 \mathrm{~cm}, B C=10 \mathrm{~cm} \) and \( A C=6 \mathrm{~cm} \). Find the area of \( \triangle A B C \). Also, find the length of \( A D \).