Q.

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:          [2024]

1 3041  
2 2541  
3 25  
4 85  

Ans.

(1)

Lines L1 and L2 trisect the line 4x + 5y = 20.

x1 = 5 × 1 + 0 × 21 + 2 = 53

y1 = 0 × 1 + 4 × 21 + 2 = 83

(x1, y1)  (53, 83)

Similarly,

x2 = 0 × 1 + 5 × 21 + 2 = 103

y2 = 4 × 1 + 0 × 21 + 2 = 43, (x2, y2)  (103, 43)

Slope of line L1 : m1 = 83 × 35 = 85

Slope of line L2 : m2 = 43 × 310 = 25

Tangent angle between the lines L1 and L2:

tan θ =|m1 - m21 + m1m2|= |85 - 251 + 85 × 25|= 3041