Math Is Fun Forum
You are not logged in.
- Topics: Active | Unanswered
#1 Re: Help Me ! » How Far Can You See? » 2024-09-10 07:07:05
Which part of the ship appeared?
I mean, isn't its height important too?
The height of the ship is important but perhaps not for this particular question. The problem does not give the ship's height. By the way, this problem does involve the curvature of Earth.
I will plug the data given into the formula.
d^2 + (3960)^2 = [(3960) + (6/5280)]2
Plugging that into my calculator, I get approximately 3 miles.
What do you say?
d ≈ 3 miles.
#2 Re: Help Me ! » How Far Can You See? » 2024-09-10 07:03:57
That's a fair comment. If the ship was a mile high, you'd be able to see the top long after the bottom had disappeared below the horizon. The method also disregards the curvature of the Earth and where the person's eyes are in that height figure. But it gives a good approximation for most practical purposes.
Bob
I am not criticizing KerimF. The question does not give the ship's height.
By the way, this problem does involve the curvature of Earth.
d^2 + (3960)^2 = [(3960) + (6/5280)]2
Plugging that into my calculator, I get approximately 3 miles.
What do you say?
d ≈ 3 miles.
#3 Re: Help Me ! » How Far Can You See? » 2024-09-10 05:40:04
Which part of the ship appeared?
I mean, isn't its height important too?
The question does not give the height of the ship. It is not needed to find the distance it is from shore. I will work it out later on today.
#4 Re: Help Me ! » How Far Can You See? » 2024-09-10 05:38:27
Not quite sure about the m conversion. You just need everything in the same units.
That formula works. Pythag is a part of trigonometry. I think it's the easiest and quickest method. d comes out as the straight line distance, not the curvature distance.
Bob
I will work it out later and show my effort here.
#5 Re: Help Me ! » Classifying Numbers » 2024-09-09 04:58:57
There is one more interesting category.
A number is called algebraic if it is the root of a polynomial equation with rational coefficients.
Non-algebraic numbers are called transcendental.
So sqrt(5) is (as you correctly say) irrational, but it is algebraic, being the root of x^2 - 5 = 0.
More complicated to prove: pi and e are not just irrational, but also transcendental.
Interesting facts. I did not know this information.
#6 This is Cool » Probability of No Rain » 2024-09-09 04:56:53
- harpazo65
- Replies: 1
There is a 30% chance of rain tomorrow. What is the probability of no rain tomorrow?
P(no rain tomorrow) = 1 - P(rain tomorrow).
This yields the answer of something different happening next time.
IN GENERAL:
P(something not happening tomorrow or next time) = 1 - P(something happening tomorrow or next).
Pretty cool, right?
#7 Re: Guestbook » Favorite Subject? » 2024-09-09 04:24:47
What’s your favorite subject?
Personally I’m really into math and scienceWhat about you?
Are you in the Navy? I am former Navy.
#8 Dark Discussions at Cafe Infinity » Guitar Sheet Music » 2024-09-09 03:43:32
- harpazo65
- Replies: 1
If you want to learn guitar sheet music basics, don't hesitate to ask me. I have been playing guitar since 1974. I am a professional sight reader for classical guitar and/or solo guitar. I also can help you with guitar tablature.
#9 Maths Is Fun - Suggestions and Comments » Divide Site By Courses » 2024-09-09 03:40:54
- harpazo65
- Replies: 3
I think the site should be divided by courses.
I also say that some of the forums should be removed or replaced.
Here are some forum titles to help students post in the proper place.
Forums:
Prealgebra
Algebra 1
Algebra 2
Geometry
Trigonometry
College Algebra
Precalculus
Calculus l
Calculus ll
Calculus lll
Ordinary Differential Equations
Linear Algebra
I also think several standardized exam forums are needed here.
Sample forum names:
SAT
GRE
GMAT
ASVAB
GED
CUNY
I also vote for a music forum, particularly music notation for guitar.
#10 Re: Introductions » Chinese seventh grader » 2024-09-09 03:25:58
Hi! I'm a Chinese 7th grader and I love maths. My English is not good but I think they can be understood...
Welcome to the forum. Never reveal your age in an open forum.
#11 Re: Introductions » New Grade 12 Math Student Here » 2024-09-09 03:24:24
Hello, I hope you all are doing well. My user is Numbersarehard, I'm a grade 12 math student who is currently in the trig unit. I find that the unit circle is very confusing and that the tan graph shouldn't exist (it is just too hard imo lol). I hope to find other people who are also in an advanced math such as I who may or may not be struggling with the same thing. Furthermore, I hope to meet some like-minded individuals or even some new math friends
I am over the age of 18 however, just wanted to make that known just in case. Happy mathing everyone
Welcome to the math site. Here's a big tip for you: NEVER reveal your age in an open forum.
#12 Introductions » Middle-aged Math Lover » 2024-09-09 03:22:47
- harpazo65
- Replies: 1
My name is Guido. I love math. I hope not only to learn from others here but to help out from time time. I enjoy middle school and high school mathematics. I am currently doing a self-study of college algebra by Michael Sullivan. Come along for the ride. Let's sharpen our math skills together.
#13 Re: Introductions » Hi i'm back » 2024-09-09 03:18:40
HI im back, although i've changed my name so you may not recognize me, i think my previous username was something like coolxxxxz, and i posted about proportion and something that was about how much time it takes 3 people A,B and C to complete a certain task if A and B finish it in a certain time and B and C in a different time, i believe bob helped me solve them, well i'm just trying to jog you're memory, anyways im back and hope to have just as as much of an enjoyable and educative time as before.
Welcome back to the math site. Enjoy your time here.
#14 Re: Introductions » Any 10th grader here? » 2024-09-09 03:16:57
Hello for context, i am already like 2 weeks into my summer and i just wanna know the if highschool math is hard. Thanks
Hello Irene. Welcome to the math site. I am not in 10th grade. I can help you with high school math if you get stuck.
#15 Help Me ! » How Far Can You See? » 2024-09-09 03:13:35
- harpazo65
- Replies: 9
Use the facts that the radius of Earth is 3960 miles and 1 mile = 5280 feet.
A person who is 6 feet tall is standing on the beach in Florida, and looks out onto the Atlantic Ocean. Suddenly, a ship appears on the horizon. How far is the ship from shore?
A friend suggested the following solution.
Let d = distance of ship from shore
Let r = radius of Earth
Let h = height of person
Let m = a mile in terms of feet
Here is the equation my friend developed:
d^2 + r^2 = [(r + (h/m)]^2
The formula above is basically applythe Pythagorean Theorem.
Questions
1. Is my friend right?
2. Is there an easier way to solve this problem even if it means trigonometry or graphing?
#16 Help Me ! » Find Domain...B » 2024-09-09 03:01:32
- harpazo65
- Replies: 1
Find the domain of each expression. If the domain does not exist over the real numbers, say none.
1. (x^2)/(x^2 + 1)
2. x/(x^2 - 9)
============================
Question 1
(x^2)/(x^2 + 1)
I quickly see that the denominator, when set equal to 0, leads to complex roots (domain lies outside the realm of real numbers).
So, my answer is none.
Question 2
x/(x^2 - 9)
x^2 - 9 = 0
x^2 = 9
sqrt{x^2} = sqrt{9}
x = -3, x = 3
Domain = {x | x cannot be -3 or 3}
Is any of this correct?
#17 Help Me ! » Find Domain...A » 2024-09-09 02:53:57
- harpazo65
- Replies: 1
Find the domain for each expression.
1. (x^2 + 5x - 10)/(x^3 - x)
2. (-9x^2 - x + 1)/(x^3 + x)
==============================
Question 1
(x^2 + 5x - 10)/(x^3 - x)
Set denominator to 0.
x^3 - x = 0
x(x^2 - 1) = 0
x = 0
x^2 - 1 = 0
x^2 = 1
sqrt{x^2} = sqrt{1}
x = -1, x = 1
Domain = {x | x cannot be 0, -1, or 1}
Question 2
(-9x^2 - x + 1)/(x^3 + x)
Set denominator to 0.
x^3 + x = 0
x(x^2 + 1) = 0
x = 0
x^2 + 1 = 0
When I subtract -1 from both sides of the equation, it leads to a situation involving complex numbers. The current chapter and section in the textbook does not ask for complex roots. So, I will say that x^2 + 1 is rejected.
Domain = {x | x cannot be 0}
#18 Help Me ! » Find CST (Central Standard Time) » 2024-09-09 02:40:56
- harpazo65
- Replies: 1
The current time is 12 noon CST. What time (CST) will it be 12,997 hours from now?
I know there are 24 hours in a day.
I now divide 12,997 hours ÷ 24 hours.
This leads to 541 days and 13 hours.
The remaining hours are 13 hours.
I now add 13 hours to the current time given: 12 noon + 13 hours takes me to 1 am CST.
I think this is right.
#19 Help Me ! » Undefined for Different Reasons » 2024-09-09 02:34:03
- harpazo65
- Replies: 5
Nothing a/0 (where a does not equal 0) and 0/0 are undefined, but for different reasons. Explain the different reasons.
#20 Help Me ! » Classifying Numbers » 2024-09-09 02:30:13
- harpazo65
- Replies: 2
List the numbers in set B that are natural, integers, rational, irrational amd real.
B = {-5/3, 2.060606..., 1.25, 0, 1, sqrt{5}, pi, e}
Natural: 0, 1
Integers: 0, 1
Rational: -5/3, 2.060606..., 1.25, 0, 1
Irrational: sqrt{5}, pi, e
Real: All the elements in set B are real numbers.
I think this is right.
#21 Re: Help Me ! » Domain in Set-builder Notation » 2024-09-09 02:24:04
Fair point. At the top of each post there's a list of symbols you can copy and paste. ≠ is available there. Does your phone allow you to copy any of those.
Whatever, I was happy with your answer as it had the essential bits.
Bob
I see the symbols at the top of each post. My cell phone does allow me to copy and paste the symbols here but I can copy each symbols found, for example, in Wikipedia and then post here.
#22 Re: Help Me ! » Find (B U C)^c » 2024-09-09 02:20:50
Dictionary.com defines rogue as "no longer obedient, belonging, or accepted ". 6 doesn't obey the rules as it's not in the universe.
Let's get more practice by making C = {1, 3, 4, 5}
That does change your previous answer.
Bob
It changes my previous answer because 3, 4, and 5 are in the universal set U.
#23 Re: Help Me ! » Find B^c ∩ C^c » 2024-09-09 02:18:20
As C complement is the elements not in C 6 doesn't feature whether it's there or not. But If you change 6 to 0 for example it would change the answer.
Bob
I did not know this fact.
#24 Re: Help Me ! » Roster Method » 2024-09-09 02:15:46
Roster method is a common term for just listing the elements.
While we're talking, note that order does not matter; an element is either in or not in a set.
So {a,b,c} = {b,a,c} and any other permutaion.
You are right. This is exactly stated in the textbook.
#25 Re: Help Me ! » Roster Method » 2024-09-08 08:39:38
OK
B
Wonderful. This is it as far as set theory is concerned. In the future, I will do a self-study of set theory as I find the course fascinating.