Advertisements
Advertisements
Question
One vertex of the equilateral triangle with centroid at the origin and one side as x + y – 2 = 0 is ______.
Options
(–1, –1)
(2, 2)
(–2, –2)
(2, –2)
Advertisements
Solution
One vertex of the equilateral triangle with centroid at the origin and one side as x + y – 2 = 0 is (–2, –2).
Explanation:
Let ABC be an equilateral triangle with vertex (x1, y1).
AD ⊥ BC and let (a, b) be the coordinates of D.
Given that the centroid G lies at the origin i.e., (0, 0)
Since, the centroid of a triangle,divides the median in the ratio 1 : 2
So, 0 = `(1 xx x_1 + 2 xx a)/(1 + 2)`
⇒ x1 + 2a = 0 ......(i)
And 0 = `(1 xx y_1 + 2 xx b)/(1 + 2)`
⇒ y1 + 2b = 0 ......(ii)
Equations of BC is given by x + y – 2 = 0 .....(iii)
Point D(a, b) lies on the line x + y – 2 = 0
So a + b – 2 = 0
Slope of equation (iii) is = – 1
And the slope of AG = `(y_1 - 0)/(x_1 - 0) = y_1/x_1`
Since, they are perpendicular to each other
∴ `- 1 xx y_1/x_1` = – 1
⇒ y1 = x1
From eq. (i) and (ii) we get
x1 + 2a = 0
⇒ 2a = – x1
y1 + 2b = 0
⇒ 2b = – y1
∴ a = b
From equation (iv) we get
a + b – 2 = 0
⇒ a + a – 2 = 0
⇒ 2a – 2 = 0
⇒ a = 1 and b = 1 ....[∵ a = b]
∴ x1 = – 2 × 1 = – 2
And y1 = – 2 × 1 = – 2
APPEARS IN
RELATED QUESTIONS
Without using the Pythagoras theorem, show that the points (4, 4), (3, 5) and (–1, –1) are the vertices of a right angled triangle.
Consider the given population and year graph. Find the slope of the line AB and using it, find what will be the population in the year 2010?
Find the values of k for which the line (k–3) x – (4 – k2) y + k2 –7k + 6 = 0 is
- Parallel to the x-axis,
- Parallel to the y-axis,
- Passing through the origin.
Find the slope of the lines which make the following angle with the positive direction of x-axis:
\[\frac{2\pi}{3}\]
State whether the two lines in each of the following is parallel, perpendicular or neither.
Through (6, 3) and (1, 1); through (−2, 5) and (2, −5)
Using the method of slope, show that the following points are collinear A (4, 8), B (5, 12), C (9, 28).
What can be said regarding a line if its slope is zero ?
Show that the line joining (2, −3) and (−5, 1) is parallel to the line joining (7, −1) and (0, 3).
Prove that the points (−4, −1), (−2, −4), (4, 0) and (2, 3) are the vertices of a rectangle.
Without using the distance formula, show that points (−2, −1), (4, 0), (3, 3) and (−3, 2) are the vertices of a parallelogram.
Find the angle between the X-axis and the line joining the points (3, −1) and (4, −2).
Find the equation of a straight line with slope −2 and intersecting the x-axis at a distance of 3 units to the left of origin.
Find the equations of the straight lines which cut off an intercept 5 from the y-axis and are equally inclined to the axes.
The line through (h, 3) and (4, 1) intersects the line 7x − 9y − 19 = 0 at right angle. Find the value of h.
Find the acute angle between the lines 2x − y + 3 = 0 and x + y + 2 = 0.
Find the angle between the line joining the points (2, 0), (0, 3) and the line x + y = 1.
Find the tangent of the angle between the lines which have intercepts 3, 4 and 1, 8 on the axes respectively.
Show that the line a2x + ay + 1 = 0 is perpendicular to the line x − ay = 1 for all non-zero real values of a.
Write the coordinates of the image of the point (3, 8) in the line x + 3y − 7 = 0.
The acute angle between the medians drawn from the acute angles of a right angled isosceles triangle is
The medians AD and BE of a triangle with vertices A (0, b), B (0, 0) and C (a, 0) are perpendicular to each other, if
The equation of the line with slope −3/2 and which is concurrent with the lines 4x + 3y − 7 = 0 and 8x + 5y − 1 = 0 is
The reflection of the point (4, −13) about the line 5x + y + 6 = 0 is
If x + y = k is normal to y2 = 12x, then k is ______.
Point of the curve y2 = 3(x – 2) at which the normal is parallel to the line 2y + 4x + 5 = 0 is ______.
If the line joining two points A(2, 0) and B(3, 1) is rotated about A in anticlock wise direction through an angle of 15°. Find the equation of the line in new position.
If one diagonal of a square is along the line 8x – 15y = 0 and one of its vertex is at (1, 2), then find the equation of sides of the square passing through this vertex.
The two lines ax + by = c and a′x + b′y = c′ are perpendicular if ______.
The reflection of the point (4, – 13) about the line 5x + y + 6 = 0 is ______.
Find the equation of the line passing through the point (5, 2) and perpendicular to the line joining the points (2, 3) and (3, – 1).
The equation of the straight line passing through the point (3, 2) and perpendicular to the line y = x is ______.
Equations of the lines through the point (3, 2) and making an angle of 45° with the line x – 2y = 3 are ______.
The points (3, 4) and (2, – 6) are situated on the ______ of the line 3x – 4y – 8 = 0.
If the vertices of a triangle have integral coordinates, then the triangle can not be equilateral.
The vertex of an equilateral triangle is (2, 3) and the equation of the opposite side is x + y = 2. Then the other two sides are y – 3 = `(2 +- sqrt(3)) (x - 2)`.
The line `x/a + y/b` = 1 moves in such a way that `1/a^2 + 1/b^2 = 1/c^2`, where c is a constant. The locus of the foot of the perpendicular from the origin on the given line is x2 + y2 = c2.
The line which passes through the origin and intersect the two lines `(x - 1)/2 = (y + 3)/4 = (z - 5)/3, (x - 4)/2 = (y + 3)/3 = (z - 14)/4`, is ______.
A ray of light coming from the point (1, 2) is reflected at a point A on the x-axis and then passes through the point (5, 3). The co-ordinates of the point A is ______.
