Question

What is the acute angle between the lines represented by the equations $$y - \sqrt 3 x - 5 = 0$$    and $$\sqrt 3 y - x + 6 = 0\,?$$

A. $${30^ \circ }$$  
B. $${45^ \circ }$$
C. $${60^ \circ }$$
D. $${75^ \circ }$$
Answer :   $${30^ \circ }$$
Solution :
$$\eqalign{ & y - \sqrt 3 x - 5 = 0{\text{ line one}} \cr & \sqrt 3 y - x + 6 = 0{\text{ line two}} \cr & y = mx + c \cr & y = \sqrt 3 x + 5 \cr & y = \frac{x}{{\sqrt 3 }} - \frac{6}{{\sqrt 3 }} \cr & {m_1} = \sqrt 3 \cr & {m_2} = \frac{1}{{\sqrt 3 }} \cr} $$
Angle between two lines,
$$\eqalign{ & \tan \,\theta = \left| {\frac{{{m_1} - {m_2}}}{{1 + {m_1}{m_2}}}} \right| = \left| {\frac{{\sqrt 3 - \frac{1}{{\sqrt 3 }}}}{{1 + \sqrt 3 \frac{1}{{\sqrt 3 }}}}} \right| = \frac{1}{{\sqrt 3 }} = \tan \,{30^ \circ } \cr & \therefore \,\theta = {30^ \circ } \cr} $$

Releted MCQ Question on
Geometry >> Straight Lines

Releted Question 1

The points $$\left( { - a, - b} \right),\left( {0,\,0} \right),\left( {a,\,b} \right)$$     and $$\left( {{a^2},\,ab} \right)$$  are :

A. Collinear
B. Vertices of a parallelogram
C. Vertices of a rectangle
D. None of these
Releted Question 2

The point (4, 1) undergoes the following three transformations successively.
(i) Reflection about the line $$y =x.$$
(ii) Translation through a distance 2 units along the positive direction of $$x$$-axis.
(iii) Rotation through an angle $$\frac{p}{4}$$ about the origin in the counter clockwise direction.
Then the final position of the point is given by the coordinates.

A. $$\left( {\frac{1}{{\sqrt 2 }},\,\frac{7}{{\sqrt 2 }}} \right)$$
B. $$\left( { - \sqrt 2 ,\,7\sqrt 2 } \right)$$
C. $$\left( { - \frac{1}{{\sqrt 2 }},\,\frac{7}{{\sqrt 2 }}} \right)$$
D. $$\left( {\sqrt 2 ,\,7\sqrt 2 } \right)$$
Releted Question 3

The straight lines $$x + y= 0, \,3x + y-4=0,\,x+ 3y-4=0$$         form a triangle which is-

A. isosceles
B. equilateral
C. right angled
D. none of these
Releted Question 4

If $$P = \left( {1,\,0} \right),\,Q = \left( { - 1,\,0} \right)$$     and $$R = \left( {2,\,0} \right)$$  are three given points, then locus of the point $$S$$ satisfying the relation $$S{Q^2} + S{R^2} = 2S{P^2},$$    is-

A. a straight line parallel to $$x$$-axis
B. a circle passing through the origin
C. a circle with the centre at the origin
D. a straight line parallel to $$y$$-axis

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Straight Lines


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