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asambeis [7]
3 years ago
9

Find the values of θ at which there are horizontal tangent lines on the graph of r = 1 + cos θ.

Mathematics
1 answer:
Amiraneli [1.4K]3 years ago
7 0

Answer:

θ = π/3 and 5π/3

Step-by-step explanation:

x = r cos θ and y = r sin θ.  Therefore:

dy/dx = (dy/dθ) / (dx/dθ)

dy/dx = (r cos θ + r' sin θ) / (-r sin θ + r' cos θ)

In this case, r = 1 + cos θ and r' = -sin θ.

dy/dx = ((1 + cos θ) cos θ + (-sin θ) sin θ) / (-(1 + cos θ) sin θ + (-sin θ) cos θ)

dy/dx = (cos θ + cos²θ − sin²θ) / (-sin θ − sin θ cos θ − sin θ cos θ)

dy/dx = (cos θ + cos²θ − (1 − cos²θ)) / (-sin θ (1 + 2 cos θ))

dy/dx = (cos θ + 2 cos²θ − 1) / (-sin θ (1 + 2 cos θ))

The tangent line is horizontal when the numerator of dy/dx is 0 and the denominator of dy/dx is not 0.

0 = 2 cos²θ + cos θ − 1

0 = (cos θ + 1) (2 cos θ − 1)

cos θ = -1 or 1/2

θ = π/3, π, 5π/3

0 = -sin θ (1 + 2 cos θ)

sin θ = 0 or cos θ = -1/2

θ = 0, 2π/3, π, 4π/3

Therefore, the answer is θ = π/3 and 5π/3.

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The ratio of boys to girls in a school is 5:4. if there are 500 girls , how many boys are there in the school?
lana [24]

Answer:

The number of boys in the school is;

625

Explanation:

Given that the ratio of boys to girls in a school is 5:4;

5\colon4

And there are 500 girls in the school.

The number of boys in the school will be;

\begin{gathered} \frac{B}{G}=\frac{5}{4} \\ G=500 \\ B=\frac{5\times G}{4}=\frac{5\times500}{4} \\ B=625 \end{gathered}

Therefore, the number of boys in the school is;

625

3 0
1 year ago
Which rate should be used to convert 15 yards:1 feet per hour?
Lena [83]

Answer:

B.

Step-by-step explanation:

1 yard:3 feet.

8 0
2 years ago
Use Fermat's Little Theorem to determine 7^542 mod 13.
m_a_m_a [10]

a^{p-1} \equiv 1 \pmod p where p is prime, a\in\mathbb{Z} and a is not divisible by p.

7^{13-1}\equiv 1 \pmod {13}\\7^{12}\equiv 1 \pmod {13}\\\\542=45\cdot12+2\\\\7^{45\cdot 12}\equiv 1 \pmod {13}\\7^{45\cdot 12+2}\equiv 7^2 \pmod {13}\\7^{542}\equiv 49 \pmod{13}

4 0
3 years ago
Read 2 more answers
Jason has x nickels and y dimes. He has no less than 15 coins worth a maximum of $1 combined. Solve this system of inequalities
Juli2301 [7.4K]

Answer:

x + y <u>></u> 15

10x + 5y <u><</u> 100

we will put it in terms of y

y <u>></u> 15 - x

and

5y <u><</u> 100 - 10x

y <u><</u> 20 - 2x

<u>-TheUnknownScientist</u>

4 0
3 years ago
ABCD is a parallelogram. If mZCDA = 63, then mZABC = _?_ The diagram is not to scale.
nevsk [136]

Answer:

b. 63

Step-by-step explanation:

A Parallelogram is known to be a flat shape quadrilateral which has four opposite sides Each two opposite sides are parallel and are equal in length. The opposite angles are equal.

The above answer is correct because opposite angles of a parallelogram are equal:

m∠CDA = m∠ABC

where m∠CDA = 63

∴ m∠ABC = 63 (answer)

4 0
3 years ago
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