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2 years ago

What is an equation of the line that passes through the point (1,-3) and is perpendicular to the line x+3y=21?

Mathematics

1 answer:

andreev551 [17]2 years ago

7 0

Answer:

3x - y = 6

Step-by-step explanation:

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

Given

x + 3y = 21 ( subtract x from both sides )

3y = - x + 21 ( divide all terms by 3 )

y = - $\frac{1}{3}$ x + 7 ← in slope- intercept form

with slope m = - $\frac{1}{3}$

Given a line with slope m then the slope of a line perpendicular to it is

$m_{perpendicular}$ = - $\frac{1}{m}$ = - $\frac{1}{-\frac{1}{3} }$ = 3 , thus

y = 3x + c ← is the partial equation

To find c , substitute (1, - 3) into the partial equation

- 3 = 3 + c ⇒ c = - 3 - 3 = - 6

y = 3x - 6 ← in slope- intercept form

subtract y from both sides

0 = 3x - y - 6 ( add 6 to both sides )

6 = 3x - y , that is

3x - y = 6 ← in standard form

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2 years ago

What is the area of the composite figure shown

Greeley [361]

So, We Know That The Figure Shown Is A Square. So, We Need To Find The Area:
70*70 = 4900.

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2 years ago

Rewrite the following integral in spherical coordinates.

lora16 [44]

In cylindrical coordinates, we have $r^2=x^2+y^2$ , so that

$z = \pm \sqrt{2-r^2} = \pm \sqrt{2-x^2-y^2}$

correspond to the upper and lower halves of a sphere with radius $\sqrt2$ . In spherical coordinates, this sphere is $\rho=\sqrt2$ .

$1 \le r \le \sqrt2$ means our region is between two cylinders with radius 1 and $\sqrt2$ . In spherical coordinates, the inner cylinder has equation

$x^2+y^2 = 1 \implies \rho^2\cos^2(\theta) \sin^2(\phi) + \rho^2\sin^2(\theta) \sin^2(\phi) = \rho^2 \sin^2(\phi) = 1 \\\\ \implies \rho^2 = \csc^2(\phi) \\\\ \implies \rho = \csc(\phi)$

This cylinder meets the sphere when

$x^2 + y^2 + z^2 = 1 + z^2 = 2 \implies z^2 = 1 \\\\ \implies \rho^2 \cos^2(\phi) = 1 \\\\ \implies \rho^2 = \sec^2(\phi) \\\\ \implies \rho = \sec(\phi)$

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$\csc(\phi) = \sec(\phi) \implies \tan(\phi) = 1 \implies \phi = \dfrac\pi4+n\pi$

where $n\in\Bbb Z$ . Then $\frac\pi4\le\phi\le\frac{3\pi}4$ .

The volume element transforms to

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