Let A =(0,5) F ( 3, 0)
Slope of AB = -5/3
Equation of line through this segment = y = -(5/3)x + 5
Let E = ( 0,3) B = ( 7,0)
Slope of BE = -3/7
Equation of line through BE
y = (-3/7)x + 3
Find D = the intersection of these two lines
(-5/3)x + 5 = (-3/7)x + 3
5 -3 = ( 5/3 - 3/7)x
2 = (26/21)x
x = 21/13
y= (-3/7)(21/13) + 3
y = 30/13
Slope of AB = -5/7
Equation of line through AB
y= (-5/7)x + 5 Put into standard form
7y= -5x + 35
5x + 7y - 35 = 0
Distance from D to AB is given by
l 5 (21/13) + 7 (30/13) -35 l 140/13 140 / [ 13sqrt (74) ] = altitude of ADB
_________________________ = _________ =
sqrt ( 5^2 + 7^2) sqrt ( 74)
AB length = sqrt [ 5^2 + 7^2] = sqrt (74)
Area of ADB = (1/2) AB * altitude =
(1/2) sqrt (74) * 140 / ( 13 sqrt (74) ) = 140/26 = 70/13