Question

Equation of the straight line passing through the origin and making with x-axis an angle twice the size of the angle made by the line y = 0.4x is

• A. y = 0.8x
• B. $y = \frac{5}{12}x$
• C. 20x – 29y = 0
• D. 20x – 21y = 0

Answer 1

Answer: (D)

20x – 21y = 0

Answer 2

Q y = 0.4x Ž y = 2/5 x

\ tan2q = $\frac{2\tan\theta}{1 - \tan^{2}\theta}$ =$\frac{4/5}{1 - (4/25)}$= $\frac{20}{21}$