Misc 4 - Chapter 11 Class 12 Three Dimensional Geometry

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Misc 4 (Introduction) Find the equation of a line parallel to x-axis and passing through the origin. x axis makes an angle 0 with x axis, 90 with y axis & 90 with z axis. So, = 0 , = 90 , = 90 Direction cosines are l = cos 0 , m = cos 90 , n = cos 90 l = 1 , m = 0, n = 0 Direction cosines of x axis are 1, 0, 0. Misc 4 Find the equation of a line parallel to x-axis and passing through the origin. Equation of a line passing through (x1, y1, z1) and parallel to a line with direction ratios a, b, c is = = Since line passes through origin ie. (0, 0, 0), x1 = 0, y1 = 0, z1 = 0 Since line is parallel to x axis, = 1, b = 0, c = 0 Equation of line : 0 1 = 0 0 = 0 0 = =