मराठी

Equation of Tangent and Condition of Tangency

Advertisements

Topics

Estimated time: 4 minutes
Maharashtra State Board: Class 12

Key Points: Equation of Tangent and Condition of Tangency

For Standard Circle: x² + y² = a²

Sr. No. Description Formula
i. Tangent at a point (x₁, y₁) xx₁ + yy₁ = a²
ii. Parametric form of tangent at P(θ) x cosθ + y sinθ = a
iii. Condition of tangency for the line y = mx + c \[\mathrm{c=\pm a~\sqrt{1+m^{2}}}\]
  Point of contact \[\left(\frac{-\mathrm{a}^{2}\mathrm{m}}{\mathrm{c}},\frac{\mathrm{a}^{2}}{\mathrm{c}}\right)\]
iv. Equation of tangent in terms of its slope m \[y=\mathrm{m}x\pm\mathrm{a}\sqrt{1+\mathrm{m}^{2}}\]
v. Length of tangent from the point (x₁, y₁) \[\sqrt{S_{1}}=\sqrt{x_{1}^{2}+y_{1}^{2}-a^{2}}\]
vi. Equation of the Director circle x² + y² = 2a²

For General Circle: x² + y² + 2gx + 2fy + c = 0

Sr. No. Description Formula
i. Tangent at a point (x₁, y₁) xx₁ + yy₁ + g(x + x₁) + f(y + y₁) + c = 0
ii. Length of tangent from the point (x₁, y₁) \[\sqrt{S_{1}}=\sqrt{x_{1}^{2}+y_{1}^{2}+2gx_{1}+2fy_{1}+c}\]

Number of Common Tangents:

Case Diagram No. of Tangents Condition
Disjoint circles 4 d > r₁ + r₂
Touch externally 3 d = r₁ + r₂
Intersecting circles 2 d < r₁ + r₂
Touch internally 1 d = \[\left|\mathbf{R}_{1}-\mathbf{R}_{2}\right|\]
Concentric circles 0 d = 0

Equation of a pair of tangents:

(x² + y² − a²)(x₁² + y₁² − a²) = (xx₁ + yy₁ − a²)²

Advertisements
Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×