Posted by katrina on .
Plot the points A(2,2), B(4,6),C(10,2)Notice that these points are vertices of a right triangle (the angle is 90 degrees).
Find the area of the triangle ABC:

math 
Henry,
A(2, 2), B(4, 6), C(10, 2).
(AB)^2 = (4 2)^2 + (6 2 )^2,
(AB)^2 = = 4 + 16 = 20.
AB=sqrt20 = sqrt(4*5) = 2*sqrt5 = 4.47.
(BC)^2 = (10 4)^2 + (2 6)^2,
(BC)^2 = 36 + 64 = 100,
BC = sqrt100 = 10.
(AC)^2 = (10 2)^2 + (2 2)^2,
(AC)^2 = 64 + 16 = 80,
AC=sqrt80 = sqrt(16*5) = 4*sqrt5=8.94.
A = AC * AB / 2,
A=4sqrt5 * 2sqrt5/2 = 8 * 5 / 2=20.