ncert cbse chapter 10 straight lines miscellaneous exercise
11. Find the equation of the lines through the point (3, 2) which make an angle of 45 degrees with the line x – 2y = 3.
let m be the slope of the required line
using formula slope = [(- coefficient of x) / (coefficient of y)]
Slope of the given line [ x – 2y = 3 ]
is m2 = [(-1)/(-2)] = [1/2]
using formula for angle between two lines
tanu = | [m1 - m2] / [ 1 + m1*m2]|
given angle is 45 degrees
tan(45 degrees) = | [m - (1/2)] / [ 1 + m*(1/2)]|
1 = | [2m-1] / [2+m] |
because of the absolute value sign
(+1) = [2m-1] / [2+m] OR (-1) = [2m-1] / [2+m]
solving
2+m = 2m -1 or -2-m = 2m-1
m=3 or m=(-1/3)
Required line passes through (3, 2)
using point slope form
equation is
[y-2] =[3][x-3] or [y-2] =[(-1/3)][x-3]
y-2 =3x-9 or 3y-6 =(- x)+3
3x-y-7=0 or x+3y-9=0
ncert cbse chapter 10 straight lines miscellaneous exercise
24. A person standing at the junction (crossing) of two straight paths represented by the equations 2x – 3y + 4 = 0 and 3x + 4y – 5 = 0 wants to reach the path whose equation is 6x – 7y + 8 = 0 in the least time. Find equation of the path that he should follow.
22. A ray of light passing through the point (1, 2) reflects on the
x-axis at point A and the reflected ray passes through the point (5, 3).
Find the coordinates of A.
21. Find equation of the line which is equidistant from parallel lines 9x + 6y – 7 = 0 and 3x + 2y + 6 =0
Find the image of the point (3, 8) with respect to the line x +3y = 7 assuming the
line to be a plane mirror.
11. Find the equation of the lines through the point (3, 2) which make an angle of 45 degrees with the line x – 2y = 3.
ncert cbse chapter 9 sequences and series miscellaneous exercise
32.
150 workers were engaged to finish a job in a certain number of days. 4 workers dropped out on the second day. 4 more workers dropped out on the third day and so on. It took 8 more days to finish the work. Find the number of days in which the work was finished
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