Math Problem Statement

solve for t

Find equations of the tangents to the curve x = 9t^2 + 3, y = 6t^3 + 3 that pass through the point (12, 9).

Solution

To find the equations of the tangents to the curve x=9t2+3x = 9t^2 + 3, y=6t3+3y = 6t^3 + 3 that pass through the point (12,9)(12, 9), we can proceed with the following steps:

  1. Find the derivative dydx\frac{dy}{dx}: Since xx and yy are both given in terms of tt, we can find dxdt\frac{dx}{dt} and dydt\frac{dy}{dt} and then use the chain rule to find dydx\frac{dy}{dx} as: dydx=dydtdxdt\frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}}

  2. Calculate dxdt\frac{dx}{dt} and dydt\frac{dy}{dt}:

    • For x=9t2+3x = 9t^2 + 3: dxdt=18t\frac{dx}{dt} = 18t
    • For y=6t3+3y = 6t^3 + 3: dydt=18t2\frac{dy}{dt} = 18t^2

    Therefore, dydx=18t218t=t\frac{dy}{dx} = \frac{18t^2}{18t} = t

  3. Find points on the curve (x,y)(x, y) in terms of tt: Substitute values of tt into the parametric equations x=9t2+3x = 9t^2 + 3 and y=6t3+3y = 6t^3 + 3 to obtain points on the curve.

  4. Set up the tangent line equation: The slope of the tangent line at any point tt is tt. The equation of the tangent line passing through the point on the curve can be written as: y(6t3+3)=t(x(9t2+3))y - (6t^3 + 3) = t (x - (9t^2 + 3))

  5. Solve for tt such that the tangent line passes through (12,9)(12, 9): Substitute x=12x = 12 and y=9y = 9 into the tangent line equation: 9(6t3+3)=t(12(9t2+3))9 - (6t^3 + 3) = t (12 - (9t^2 + 3)) Simplify and solve for tt.

Let me go through these calculations and solve for tt.The values of tt that satisfy the condition for the tangent to pass through the point (12,9)(12, 9) are t=2t = -2 and t=1t = 1.

Would you like me to proceed by finding the explicit equations of the tangent lines at these values of tt?

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Math Problem Analysis

Mathematical Concepts

Calculus
Parametric Equations
Derivatives
Tangent Lines

Formulas

Derivative of parametric equations dy/dx = (dy/dt) / (dx/dt)
Equation of a tangent line: y - y1 = m(x - x1)

Theorems

Chain Rule in differentiation

Suitable Grade Level

Grades 11-12