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avatar+1439 
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We want to find the exponential form of the complex number:

 

\[
e^{\frac{17\pi i}{60}} + e^{\frac{27\pi i}{60}} + e^{\frac{37\pi i}{60}} + e^{\frac{47\pi i}{60}} + e^{\frac{57\pi i}{60}}
\]

 

### Step 1: Recognize the terms as roots of unity


The terms \( e^{\frac{17\pi i}{60}}, e^{\frac{27\pi i}{60}}, e^{\frac{37\pi i}{60}}, e^{\frac{47\pi i}{60}}, e^{\frac{57\pi i}{60}} \) are all complex numbers in exponential form. Notice that these exponents can be expressed as:

 

\[
\frac{17\pi i}{60}, \frac{27\pi i}{60}, \frac{37\pi i}{60}, \frac{47\pi i}{60}, \frac{57\pi i}{60}
\]

 

These correspond to angles \( \theta = \frac{17\pi}{60}, \frac{27\pi}{60}, \frac{37\pi}{60}, \frac{47\pi}{60}, \frac{57\pi}{60} \).

 

Since \( e^{i\theta} \) represents a point on the unit circle in the complex plane, each of these terms can be considered as specific roots of unity, although not all are primitive roots.

 

### Step 2: Consider the sum of the angles


The sum can be expressed as:

 

\[
S = e^{\frac{17\pi i}{60}} + e^{\frac{27\pi i}{60}} + e^{\frac{37\pi i}{60}} + e^{\frac{47\pi i}{60}} + e^{\frac{57\pi i}{60}}
\]

 

These angles are evenly spaced on the unit circle by an angle increment of \( \frac{10\pi}{60} = \frac{\pi}{6} \).

 

### Step 3: Utilize symmetry


These angles correspond to the roots of the equation \( x^5 - 1 = 0 \) rotated by a small angle \( \frac{17\pi}{60} \). The angles \( \frac{17\pi}{60}, \frac{27\pi}{60}, \frac{37\pi}{60}, \frac{47\pi}{60}, \frac{57\pi}{60} \) map to the five vertices of a regular pentagon inscribed in the unit circle but rotated slightly.

 

For a regular \( n \)-gon (in this case, \( n = 5 \)), the sum of vectors corresponding to the vertices is zero if the vectors are evenly distributed around the circle (because they symmetrically cancel each other out). However, here, the vertices are slightly rotated, but they are still symmetrically spaced around the circle.

 

### Step 4: Apply properties of roots of unity


Given the symmetry and spacing:

 

\[
S = e^{i\frac{\theta_0}{60}} \cdot \left(1 + e^{i\frac{2\pi}{5}} + e^{i\frac{4\pi}{5}} + e^{i\frac{6\pi}{5}} + e^{i\frac{8\pi}{5}}\right)
\]

 

Where \( \theta_0 \) is \( \frac{17\pi}{60} \), and the roots sum to zero because they represent the vertices of a pentagon. Thus, the sum

:

\[
S = 0
\]

 

### Conclusion:


The exponential form of the given complex number is:

 

\[
\boxed{0}
\]

Aug 16, 2024
 #2
avatar+1439 
+1

Given that triangle \(ABC\) has altitudes \(AD = 14\), \(BE = 16\), and \(CF = h\), where \(h\) is a positive integer, we need to find the largest possible value of \(h\).

 

### Step 1: Use the area formula with altitudes


The area of triangle \(ABC\) can be expressed in terms of the altitudes and the corresponding sides:

 

\[
\text{Area} = \frac{1}{2} \times a \times h_a = \frac{1}{2} \times b \times h_b = \frac{1}{2} \times c \times h_c
\]

 

where \(h_a = AD\), \(h_b = BE\), and \(h_c = CF = h\), and \(a\), \(b\), and \(c\) are the lengths of the sides opposite the vertices \(A\), \(B\), and \(C\), respectively.

 

### Step 2: Express the sides in terms of the area and altitudes


Let the area of triangle \(ABC\) be denoted as \(K\). Then:

 

\[
K = \frac{1}{2} \times a \times 14 = 7a
\]


\[
K = \frac{1}{2} \times b \times 16 = 8b
\]


\[
K = \frac{1}{2} \times c \times h = \frac{1}{2}ch
\]

 

### Step 3: Equate the expressions for the area \(K\)


From the first two equations:

 

\[
7a = 8b \quad \Rightarrow \quad a = \frac{8b}{7}
\]

 

Using the equation for \(K\) involving \(h\):

 

\[
7a = \frac{1}{2} ch
\]

 

Substitute \(a = \frac{8b}{7}\) into the equation:

 

\[
7\left(\frac{8b}{7}\right) = \frac{1}{2}ch
\]

 

Simplify:

 

\[
8b = \frac{1}{2}ch
\]

 

Multiply both sides by 2:

 

\[
16b = ch
\]

 

Thus:

 

\[
h = \frac{16b}{c}
\]

 

### Step 4: Maximize \(h\)


We aim to maximize \(h = \frac{16b}{c}\), where \(b\) and \(c\) are positive integers.

 

Recall that \(K = 7a = 8b = \frac{1}{2}ch\). We want to maximize \(h\), so:

 

\[
c = \frac{16b}{h}
\]

 

To maximize \(h\), minimize \(c\). Since \(b = 7\), \(a = 8\), choose \(b = 7\) and \(c = 1\) which gives:

 

\[
h = \frac{16 \times 7}{1} = 112
\]

 

However, since \(b = \gcd(7,8)\), choose \(b = 7\) for simplicity. So:

 

\[
K = 112, h = 1
]


Thus:

 

\[
h \leq 112
\]

 

### Final Answer:

 

Since \(h = 112\), the maximum value for the given maximum number is \( \boxed{112} \).

Aug 16, 2024
 #1
avatar+1897 
+1

You are missing some values in your question, but I'm gonna assume the following was asked. 

 

A machine randomly generates one of the nine numbers   1,2,3...8,9   with equal likelihood. What is the probability that when Tsuni uses this machine to generate four numbers their product is divisible by 4. Express your answer as a common fraction.

 

________________________________________________________________________________________________________________________

 

Now, since we can draw two of the same numbers and order doesn't matter, we don't do \(9\choose 4\) to find the total amount of possibilites, but instead just do

\(9 \cdot 9\cdot 9 \cdot 9 = 9^4 = 6561\)

 

Now, we can use complementary counting to find the number of cases that DO NOT work and then subtract it from 1. 

This is because it's MUCH easier to calculate odd numbers rather than even numbers. 

 

Our first case is that all 4 numbers are odd. If all 4 numbers are odd, the product is odd, therefore meaning it cannot possibly be divisble by 4. 

Since out of the 9 numbers, 5 numbers are odd, we have a \(5/9\) chance each generation that the number is odd. 

Since we need 4 odd numbers in a row, we simply have \(({5 \over 9})^4 = {625 \over 6561}\)

 

Our next case is where we get 3 odd numbers in a row and then a 2 or a 6. If we roll a 4 or 8, the product will automatically be divisble by 4. 

Thus, we have \({2 \times 5^3 \times {4 \choose 3} \over 6561} = {1000 \over 6561}\)

 

Subtracting the sum from 1, we get the final answer of \(1 - ({625 \over 6561} + {1000 \over 6561} ) = \color{brown}\boxed{4936 \over 6561}\)

 

I would like verification of the final answer, but I believe this is the correct answer. 

 

Thanks! :)

Aug 16, 2024
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