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In Class 11, the topic of straight lines is introduced in the context of coordinate geometry. Here’s an overview of what you’ll typically study:

1. **Equation of a Straight Line**: The equation of a straight line in the plane can be expressed in various forms, including:
– Slope-intercept form: $$y = mx + c$$, where $$m$$ is the slope of the line and $$c$$ is the y-intercept (the point where the line intersects the y-axis).
– Point-slope form: $$y – y_1 = m(x – x_1)$$, where $$m$$ is the slope of the line and $$(x_1, y_1)$$ is a point on the line.
– Two-point form: $$\frac{y – y_1}{y_2 – y_1} = \frac{x – x_1}{x_2 – x_1}$$, where $$(x_1, y_1)$$ and $$(x_2, y_2)$$ are two points on the line.

2. **Slope of a Line**: The slope of a line is a measure of its steepness. It is given by the ratio of the change in y-coordinates to the change in x-coordinates between two points on the line.

3. **Intercepts**: The x-intercept of a line is the point where it intersects the x-axis (i.e., where $$y = 0$$), and the y-intercept is the point where it intersects the y-axis (i.e., where $$x = 0$$).

4. **Parallel and Perpendicular Lines**: Lines with the same slope are parallel, and lines with slopes that are negative reciprocals of each other are perpendicular.

5. **Distance between a Point and a Line**: The distance between a point $$(x_0, y_0)$$ and a line $$Ax + By + C = 0$$ is given by $$\frac{|Ax_0 + By_0 + C|}{\sqrt{A^2 + B^2}}$$.

6. **Angle between Two Lines**: The angle $$\theta$$ between two lines with slopes $$m_1$$ and $$m_2$$ is given by $$\tan(\theta) = \frac{|m_2 – m_1|}{1 + m_1m_2}$$.

Understanding the properties and equations of straight lines is fundamental in mathematics and has applications in various fields, including physics, engineering, and computer graphics.