Math Is Fun Forum

Yes, that seems a good suggestion.

Two tricky problems to start the day:-

Problem # k + 10
Complete the series:-
1248, 1632, 6412, 8256, _____

Problem # k + 11
What is special about the number 2592?

The idea seems great!
Inspite of the hide tag, its too tempting for many to view the answer.
Since most of our members solve the problems and post their solutions in a day or two, I post a problem or two everyday. Once the problem is solved, I forget to tell how it is done.
Your idea would be of great help

You are correct, wcy.
Good, you didn't tell how you did it
Try earlier problems too.

Do you know why they never have beer at a math party?
Because you can't drink and derive...

Did you hear about the teacher who was arrested trying to board an airplane with a compass, a protractor and a calculator?
He was charged with carrying weapons of math instruction.

If it's zero degrees outside today and it's supposed to be twice as cold tomorrow, how cold is it going to be?

I believe five out of four people have trouble with fractions. -- Steven Wright

A teacher was trying to impress her students with the fact that terms cannot be subtracted from one another unless they are like terms. "For example," she continued, "we cannot take five apples from six bananas."
"Well," countered a pupil, "can't we take five apples from three trees?"

Question: "How many seconds are there in a year?"
Answer: "Twelve. January second, February second, March second, ..."

Q. What did one math book say to the other?
A. Don't bother me! I've got my own problems!

You Might Be a Mathematician if...
you are fascinated by the equation  e^(i*pi) +1=0

you know by heart the first fifty digits of pi.

you have tried to prove Fermat's Last Theorem.

you know ten ways to prove Pythagoras' Theorem.

your telephone number is the sum of two prime numbers.

you have calculated that the World Series actually diverges.

you are sure that differential equations are a very useful tool.

you comment to your wife that her straight hair is nice and parallel.

when you say to a car dealer "I'll take the red car or the blue one", you must add "but not both of them."

My answer

f(x) = x²/(1+x²)
f(x) = x²(1+x²)-¹
Now, use the uv method:- u'v + uv'
f'(x) = 2x(1+x²)-¹ + x²(-1)(1+x²)-²(2x)

This is because you didn't want to use u/v = (u'v - uv')/v²

In a parallelogram,
opposite sides are parallel, and equal; opposite angles are equal, and the diagonals (lines inside that intersect) bisect each other.
When you know the length of the diagonals, half of them would be the sides of a traingle they form with one of the sides of the parallelogram.

Use the theorems that (i) when two lines intersect each other, the vertically opposite angles are equal and (ii) sum of the total angles is equal to 360 degrees. This way, all the angles can be known.

Now, use the Cosine Theorem
a² = b² + c² - 2bcCosA
(where A, B, C are three angles of a traingle and a,b,c are the three sides opposite to angles A,B,C respectively)
for knowing the third side of the triangle, which forms a side of the parallelogram. Following this method, the adjacent side too can be found! Since opposite sides of a parallelogram are equal, we know all the four sides!

I know this reply is long, and may not be of much help; that's because some Mathematical problems are difficult to explain without a diagram!

Welcome to the forum, John!
Your posts and replies are interesting, keep posting

Thanks Rora, we miss you in this forum!

Mikau, Ahgua.....I am sorry, yesterday, when I was
trying to copy the diagram, I saw two same posts
(maybe, I thought I saw) of the diagram, to simplify,
I tried to delete one, and the entire post and got deleted.
I shall be much much more careful in the future,
and thanks for posting it before I requested you!

Nice question, brilliant reasoning.

Problem #k+4

A polyhedron has 12 faces(sides) and 18 edges. How many vertices does it have?