16. [8.4] Find the slope of the line containing the points \( P_{1}(-8,3) \) and \( P_{2}(-8,-1) \)

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 \( A D \).

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

Find the area of a parallelogram \( A B C D \) whose bese \( B C \) is 27 cm and altitude \( A E \) is 8 cm . If the lengh of the altitude \( A F \) to the base \( C D \) is 12 cm . Find \( C D \).

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

Si el perímetro de un círculo es \( 10 \pi \mathrm{~cm} \). ¿cuál es el área de su semicirculo?