The portion of the line 4x+5y=20 in the first quadrant is trisected by the lines L1 and L2 passing through the origin. The tangent of an angle between the lines L1 and L2 is :
(A)58
(B)4125
(C)52
(D)4130✓ Correct
Answer: (D)
Solution
The line 4x+5y=20 meets the axes at (5,0) and (0,4). Trisecting this segment gives A=(310,34) and B=(35,38).
Slopes from the origin: m1=10/34/3=52, m2=5/38/3=58.