Let a point A lie between the parallel lines L₁$L_{1}$ and L₂$L_{2}$ such that its distances from L₁$L_{1}$ and L₂$L_{2}$ are 6 and 3 units, respectively. Then the area (in sq. units) of the equilateral triangle ABC, where the points B and C lie on the lines L₁$L_{1}$ and L₂$L_{2}$ respectively, is:
A.15√(6)$15\sqrt{6}$
B.27
C.21√(3)$21\sqrt{3}$
D.12√(2)$12\sqrt{2}$
Solution & Explanation
Related Formula
Area of Equilateral Triangle = √(3)4 a²$$\text{Area of Equilateral Triangle} = \frac{\sqrt{3}}{4} a^2$$
Where a$a$ is the side length.
Core Logic
Let the side of the equilateral triangle be a$a$.
Let θ$\theta$ be the angle between the side AC$AC$ and the parallel line L₂$L_2$.
Then, the angle between the side AB$AB$ and the parallel line L₁$L_1$ can be expressed via alternate geometry. Given distances from A$A$ to the lines form right-angled triangles.
Step 1: Set up geometric projections
Equilateral triangle between parallel lines diagram for Q4 - JEE Main 2026 Morning
From vertex C$C$ to line passing through A$A$ parallel to L₁, L₂$L_1, L_2$, the perpendicular distance is 3$3$.
In the right triangle formed, we have:
θ = (3)/(a)$$\sin \theta = \frac{3}{a}$$
Similarly, point B$B$ lies on L₁$L_1$. The perpendicular distance from A$A$ to L₁$L_1$ is 6$6$.
However, combining the overall heights between the parallel lines, the total distance between L₁$L_1$ and L₂$L_2$ is 6 + 3 = 9$6 + 3 = 9$.
The projection of side BC$BC$ (which connects L₁$L_1$ and L₂$L_2$) vertically is 9$9$.
Area of Δ ABC = √(3)4 a²$$\text{Area of } \Delta ABC = \frac{\sqrt{3}}{4} a^2$$= √(3)4 × 84 = 21√(3)$$= \frac{\sqrt{3}}{4} \times 84 = 21\sqrt{3}$$
Pattern Recognition
When a rigid polygon (like an equilateral triangle or square) is wedged between parallel lines, set a base orientation angle θ$\theta$ for one edge and use rotational shifts (e.g., 60° + θ$60^{\circ} + \theta$) to project heights. Expanding the sine addition formula instantly yields the side length.
Chapter Mix
Class 11 Maths: Straight Lines
Class 11 Maths: Trigonometric Functions
Keywords:#area of the equilateral triangle#JEE Main 2026 Morning Q4#Straight Lines JEE Main 2026#Equilateral Triangle Between Parallel Lines JEE Main 2026
More Straight Lines Previous-Year Questions — Page 6
Q1jee_main_2024_30_jan_morningRotation of Axes and Lines
A line passing through the point A(9,0)$A(9,0)$ makes an angle of 30°$30^{\circ}$ with the positive direction of x-axis. If this line is rotated about A through an angle of 15°$15^{\circ}$ in the clockwise direction, then its equation in the new position is
A.y√(3) - 2 + x = 9$\frac{y}{\sqrt{3} - 2} + x = 9$
B.x√(3) - 2 + y = 9$\frac{x}{\sqrt{3} - 2} + y = 9$
C.x√(3) + 2 + y = 9$\frac{x}{\sqrt{3} + 2} + y = 9$
D.y√(3) + 2 + x = 9$\frac{y}{\sqrt{3} + 2} + x = 9$
Rotation of Axes and Lines diagram for Q1 - JEE Main 2024 Morning
The initial line makes an angle of 30°$30^{\circ}$ with the positive x-axis. It is rotated clockwise by 15°$15^{\circ}$ about the point A(9, 0)$A(9, 0)$.
The new angle made by the line with the positive direction of the x-axis is 30° - 15° = 15°$30^{\circ} - 15^{\circ} = 15^{\circ}$.
Step 1: Equation of the new line
The equation of the line passing through A(9, 0)$A(9, 0)$ with a slope of 15°$\tan 15^{\circ}$ is:
Eqⁿ: y - 0 = 15° (x - 9)$$\text{Eq}^n: y - 0 = \tan 15^{\circ} (x - 9)$$
We know that 15° = 2 - √(3)$\tan 15^{\circ} = 2 - \sqrt{3}$.
-y√(3) - 2 = x - 9$$\frac{-y}{\sqrt{3} - 2} = x - 9$$y√(3) - 2 + x = 9$$\frac{y}{\sqrt{3} - 2} + x = 9$$
Pattern Recognition
A clockwise rotation decreases the angle of inclination. Calculate the new angle, find its tangent, and carefully algebraicize the denominator to match the given option forms.
Chapter Mix
Class 11 Maths: Straight Lines
Q2jee_main_2024_31_jan_eveningCentroid and Orthocentre
Let A (a, b)$A (a, b)$, B(3, 4)$B(3, 4)$ and (-6, -8)$(-6, -8)$ respectively denote the centroid, circumcentre and orthocentre of a triangle. Then, the distance of the point P(2a + 3, 7b + 5)$P(2a + 3, 7b + 5)$ from the line 2x + 3y - 4 = 0$2x + 3y - 4 = 0$ measured parallel to the line x - 2y - 1 = 0$x - 2y - 1 = 0$ is
A.15 √(5)7$\frac{15 \sqrt{5}}{7}$
B.17√(5)6$\frac{17\sqrt{5}}{6}$
C.17 √(5)7$\frac{17 \sqrt{5}}{7}$
D.√(5)17$\frac{\sqrt{5}}{17}$
Solution
Related Formula
Centroid divides the line joining Orthocentre and Circumcentre in 2:1$$\text{Centroid divides the line joining Orthocentre and Circumcentre in } 2:1$$
Distance in parametric form: x = x₁ + r θ, y = y₁ + r θ$x = x_1 + r\cos\theta, y = y_1 + r\sin\theta$
Core Logic
Centroid and Orthocentre diagram for Q2 - JEE Main 2024 Evening
Let Orthocentre C(-6, -8)$C(-6, -8)$ and Circumcentre B(3, 4)$B(3, 4)$. Centroid A(a, b)$A(a, b)$ divides CB$CB$ in 2:1$2:1$.
So, P(2a+3, 7b+5) = (3, 5)$P(2a+3, 7b+5) = (3, 5)$.
The line along which distance is measured is parallel to x - 2y - 1 = 0$x - 2y - 1 = 0$, giving slope m = θ = (1)/(2)$m = \tan\theta = \frac{1}{2}$.
Using parametric coordinates from P(3,5)$P(3,5)$:
x = 3 + r θ, y = 5 + r θ$$x = 3 + r\cos\theta, \quad y = 5 + r\sin\theta$$
Substitute into the target line 2x + 3y - 4 = 0$2x + 3y - 4 = 0$:
Standard Euler line property: O, G, C$O, G, C$ are collinear and G$G$ divides OC$OC$ in 2:1$2:1$. Use parametric equation to find intersection distance directly without finding the intersection point.
Let A(-2, -1)$A(-2, -1)$, B(1, 0)$B(1, 0)$, C(α, β)$C(\alpha, \beta)$ and D(γ, δ)$D(\gamma, \delta)$ be the vertices of a parallelogram ABCD. If the point C lies on 2x - y = 5$2x - y = 5$ and the point D lies on 3x - 2y = 6$3x - 2y = 6$, then the value of |α + β + γ + δ|$|\alpha + \beta + \gamma + \delta|$ is equal to
Numerical Answer.Answer: 32 to 32
Solution
Related Formula
In a parallelogram, midpoints of diagonals coincide: ((xA+xC)/(2), (yA+yC)/(2)) = ((xB+xD)/(2), (yB+yD)/(2))$$\text{In a parallelogram, midpoints of diagonals coincide: } \left(\frac{x_A+x_C}{2}, \frac{y_A+y_C}{2}\right) = \left(\frac{x_B+x_D}{2}, \frac{y_B+y_D}{2}\right)$$
Core Logic
Parallelogram Properties diagram for Q23 - JEE Main 2024 Evening
Given diagonals AC$AC$ and BD$BD$ bisect each other:
Q10jee_main_2024_31_jan_morningProperties of Parallelogram
Let α, β, γ, δ in Z$\alpha, \beta, \gamma, \delta \in Z$ and let A (α, β)$A (\alpha, \beta)$, B (1, 0)$B (1, 0)$, C (γ, δ)$C (\gamma, \delta)$ and D (1, 2)$D (1, 2)$ be the vertices of a parallelogram ABCD$ABCD$. If AB = √(10)$AB = \sqrt{10}$ and the points A$A$ and C$C$ lie on the line 3y = 2x + 1$3y = 2x + 1$, then 2(α + β + γ + δ)$2(\alpha + \beta + \gamma + \delta)$ is equal to
A.10$10$
B.5$5$
C.12$12$
D.8$8$
Solution
Core Logic
Let E$E$ be the midpoint of the diagonals AC$AC$ and BD$BD$.
Since ABCD$ABCD$ is a parallelogram, the diagonals bisect each other.
Properties of Parallelogram diagram for Q10 - JEE Main 2024 Morning
Midpoint E$E$ from BD$BD$: ( (1+1)/(2), (0+2)/(2) ) = (1, 1)$\left( \frac{1+1}{2}, \frac{0+2}{2} \right) = (1, 1)$.
Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.