📐1. Coordinate Geometry (Straight Lines & Conics)
1. Straight Lines (Saral Rekha)
• Distance: $d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}$
• Slope (m): $m = \tan \theta = \frac{y_2-y_1}{x_2-x_1}$
• Angle between Lines: $\tan \theta = |\frac{m_1 - m_2}{1 + m_1m_2}|$
• Parallel: $m_1 = m_2$ | Perpendicular: $m_1m_2 = -1$
• Point to Line Distance: $d = \frac{|ax_1+by_1+c|}{\sqrt{a^2+b^2}}$
2. Circles (Vritt)
• Standard Eqn: $x^2 + y^2 + 2gx + 2fy + c = 0$
• Center: $(-g, -f)$ | Radius: $\sqrt{g^2+f^2-c}$
• Condition of Tangency: $c^2 = r^2(1+m^2)$
• Length of Tangent: $L = \sqrt{S_1}$ | Orthogonal: $2g_1g_2 + 2f_1f_2 = c_1 + c_2$
3. Conic Sections (Quick Summary)
| Feature |
Parabola ($y^2=4ax$) |
Ellipse |
Hyperbola |
| Eccentricity (e) |
$e = 1$ |
$\sqrt{1 - \frac{b^2}{a^2}}$ |
$\sqrt{1 + \frac{b^2}{a^2}}$ |
| Focus |
$(a, 0)$ |
$(\pm ae, 0)$ |
$(\pm ae, 0)$ |
| Latus Rectum |
$4a$ |
$2b^2/a$ |
$2b^2/a$ |
4. Golden Tricks for JEE
• T=0 Rule: Tangent ke liye $x^2 \to xx_1, x \to \frac{x+x_1}{2}$ replace karein.
• Director Circle: Locus of $\perp$ tangents.
- Circle: $x^2+y^2=2r^2$ | Ellipse: $x^2+y^2=a^2+b^2$
📊 Visual: Conic Sections Geometry Map