Multiple Calculus
1. Evaluate \(\int \frac{\sqrt{4x^2 - 1}}{x^2} \, dx\).
Use substitution or integration by parts combined with algebraic manipulation to solve this integral.
2. Consider the parametric equations for the hyperbola given by \(\frac{x^2}{4} - \frac{y^2}{9} = 1\).
The correct parametric form uses hyperbolic functions: \(x = 2 \cosh t, y = 3 \sinh t\).
3. Evaluate \(\int e^{-2x} \sinh x \, dx\).
Use integration by parts or rewrite \(\sinh x\) in exponential form, then integrate.
4. For the parabola described by \(x^2 - 2x + 8y = 15\), rewrite it in vertex form to find vertex, focus, and directrix.
Steps for integral \(\int \frac{\sqrt{4x^2 - 1}}{x^2} \, dx\):
1. Let \(I = \int \frac{\sqrt{4x^2 - 1}}{x^2} \, dx\).
2. Use substitution: let \(u = \sqrt{4x^2 -1}\Rightarrow u^2 = 4x^2 -1\).
3. Differentiate \(u^2\) to find \(du\) in terms of \(dx\).
4. Express everything in terms of \(u\) and simplify.
5. Integrate and back-substitute.
Answer:
$$ I = 2 \ln|2x + \sqrt{4x^2 -1}| - \frac{\sqrt{4x^2 -1}}{x} + C $$
Steps for parametric equation:
1. Recognize hyperbola standard parametric form uses hyperbolic functions.
2. \(x = 2 \cosh t, y = 3 \sinh t\) satisfy \(\frac{x^2}{4} - \frac{y^2}{9} = 1\).
Steps for \(\int e^{-2x} \sinh x \, dx\):
1. Express \(\sinh x = \frac{e^x - e^{-x}}{2}\).
2. Integrate term by term:
$$\int e^{-2x} \frac{e^x - e^{-x}}{2} \, dx = \frac{1}{2} \int (e^{-x} - e^{-3x}) \, dx$$
3. Integrate:
$$ \frac{1}{2} \left(-e^{-x} + \frac{e^{-3x}}{3} \right) + C $$
4. Simplify:
$$ -\frac{1}{2} e^{-x} + \frac{1}{6} e^{-3x} + C $$
This matches
$$ -\frac{1}{3} [e^{-2x} \cosh x + 2 e^{-2x} \sinh x] + C$$
Steps for parabola \(x^{2} - 2x + 8y = 15\):
1. Complete square for \(x^{2} - 2x\):
$$ x^2 - 2x + 1 = (x -1)^2 $$
Rewrite equation:
$$ (x -1)^2 + 8y = 16 $$
2. Rearrange:
$$ 8y = 16 - (x -1)^2 \Rightarrow y = 2 - \frac{(x-1)^2}{8} $$
3. This is a parabola with vertex at \((1, 2)\).
4. The parabola opens downward since coefficient of squared term is negative.
5. Focus and directrix found by \(4p = 8 \Rightarrow p=2\).
Focus: \((1, 2 + p) = (1,4)\).
Directrix: \(y = 2 - p = 0\).
Answer: parabola with vertex (1, 2), focus (1, 4), directrix \(y = 0\).
Final answers:
Integral: $$2 \ln |2x + \sqrt{4x^2 -1}| - \frac{\sqrt{4x^2 -1}}{x} + C$$
Parametric equations: \(x=2 \cosh t, y=3 \sinh t\).
Exponential integral: $$-\frac{1}{3} [e^{-2x} \cosh x + 2 e^{-2x} \sinh x] + C$$
Parabola with vertex at (1, 2), focus (1, 4), directrix \(y=0\).