math help. why can't i remember

mctrivia

picture not to scale.

X and Y are for 2 differen't questions and have no relationship.

For some reason I can not remember how to solve for X or Y? radius is 96



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Microcontrolled

I have a class on this tomorrow, I can help you then.

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mctrivia

well have fun with that. I know it is not difficult but I have hit a mental block.

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Phil Pilgrim (PhiPi)

x = 4 y / 3

x² + y² = 96²

x² + 16x²/ 9 = 96²

25x²/9 = 96²

5x/3 = 96

x = 288 / 5 = 57.6

-Phil

Beau Schwabe

mctrivia,

If I read your question right, I had a similar problem or need with the demo below for the inclination of the horizon...




...if it's the same sort of problem I can post my solution, or you can look at the available code from the You-Tube link or in the OBEX.

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mctrivia

Thanks. You are correct of course. Split into to triangles and use pythagrous

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rjo_

if you have two different problems, with no relationship between x and y, then let's just talk about them one at a time.

What the 3x tells us is that 3 times some number x, = 16*sin(of some angle ... lets call it z)
and we know that 4 times that same number x is equal to 16* the cosine an angle, pi/2 - z)

so, 16/3(sin z)= 16/4 * cosine(pi/2-z)

and sin (z)/cos(pi/2-z) = 4/3

but the cos(pi/2 -z) is just the sin of z... so sin(z)/sin(z) = 4/3

and we find that 1 = 4/3

rjo_

That is the first answer to the first part... but since that makes no since, there doesn't seem to be a reason to worry about the second part[noparse]:)[/noparse]

That is the way you wrote it... don't blame me[noparse]:)[/noparse]

mctrivia

I think you made a miscalculation there.

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mctrivia

Phil answered the question already. Though his answer is not right. Since 4x can not be more then 96

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Post Edited (mctrivia) : 1/22/2010 3:20:44 AM GMT

rjo_

But the question you asked is a good one... "why can't I remember math?" There are all kinds of answers for that .... but you are young... your brain is working just fine, you have no problems with relating various complex entities... you do it everyday. So, why can't you remember math?

We all have math built into our brains... and you would appear to have more than your share. The problem is that our brains all work slightly differently when it comes to math and this is probably built in at birth. So, when someone, whose math brain differs from yours tries to teach you math...he teaches from the perspective of how his brain works math and all he really does is confuse you.

The first time my first grade teacher tried to explain the equals sign to me... I knew she was wrong, and I concluded that if that is the way the whole world used the equals sign, the world was a pretty messed up place. I rejected her completely... refused to listen to her anymore. Wouldn't do the probolems. My mother got a frantic call... saying that I must be mentally retarded and they didn't know what to do with me... did she want me to go into the special ed class?

No lie... and no joke[noparse]:)[/noparse]

Rich

rjo_

When we decimate numbers... we erase the fractional equivalents that gave rise to those numbers. Trying to get me to accept that
1/3 = .3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 was pretty much impossible too[noparse]:)[/noparse]

rjo_

if we use scientific notation... how are to express a unitary difference in magnitude between two number which ends in 10^27?

rjo_

Any or all of these things might have bothered your mind. Our brains are associative... if we have a psychologically difficult experience while we are trying to learn something... whatever it is we are trying to learn will be linked to that experience. Fortunately, all experience seems to have a "half-life." So, the farther we are from that experience, the easier it is to revisit whatever it was that we had trouble learning because of the associative properties of the brain.

rjo_

And of course I made a math error in my response[noparse]:)[/noparse] the cosine isn't a cosine[noparse]:)[/noparse] But the rest of it, you can take to the bank[noparse]:)[/noparse]

Phil Pilgrim (PhiPi)

mctrivia said...
Phil answered the question already. Though his answer is not right. Since 4x can not be more then 96

Your "question" was pretty ambiguously expressed. It would have been better to use a and b, so as not to be confused with Cartesian coordinates. Now that I see what you're after, let's go again:

(4x)² + (3x)² = 96²

16x² + 9x² = 96²

25x² = 96²

5x = 96

x = 96 / 5 = 19.2

Similarly for y. Better?

-Phil

Post Edited (Phil Pilgrim (PhiPi)) : 1/22/2010 3:57:25 AM GMT

mctrivia

that is correct. for those that are not sure why here is how phil is looking at it. makes it much easier to see the answer.



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mctrivia

rjo_ i think the problem is just some times you get stuck in a rut looking at things the wrong way and need someone to point out that if you just split the square in half the answer will become obvious.

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rjo_

I thought it was a good question "why can't I remember____" .

People ask themselves this question all of the time. When people are filtering through the forum to see what to read... they will open your thread, because of the title. The specific math question deserves a specific answer. But for me, the general question will have more resonance with lots of people. Some of the smartest kids never make it out of high school. Some of them are here and will read your thread.

I admire your work.

Rich

erco

Lower angle a= inv tan (3/4)
a=36.870
4x=96*cos(a)......... x=19.2
also
3x=96*sin(a) ..........x=19.2

@Phil: Have you done the "crossed ladder problem"? Good brain scratcher. Google it.

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Cluso99

There is however an easier solution. You should remember that a right angled triangle with sides 3, 4 has a hypotenuse of 5 (the 3,4,5 triangle - the other one to remember is 1,1 and 1.414 [noparse][[/noparse]sqrt of 2]). Of course this could be calculated using Pythagorus theorem.

Therefore using the last pic posted my mctrivia it can be seen 5x=96, so x=96/5=19.2 So, it is much simpler than using sin/cos/squares.

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Phil Pilgrim (PhiPi)

mctrivia,

This wouldn't have anything to do with comparing the sizes of standard vs. widescreen TVs/LCDs, would it?

-Phil

mctrivia

Yes phili it does

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RichK

Ok, I didn't read Cluso before I posted this. He of course got the answer first.

Sorry

It's a standard 3-4-5 right triangle. I use it to square up framing all the time. Or in this case 3x-4x-5x. The result is then that the radius is = 5x so x=96/5. I think that is what Phil ended up with

Rich.

erco

McTrivia, if you can afford a 96" TV, you can afford to pay someone to do your math for you! [noparse]:)[/noparse]

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mctrivia

Nope can't afford 96" tv. Try make a 96*2 pixel tv

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stephenwagner

Hint,

Its a clasic 3 4 5 triangle.

SJW

mctrivia

Only x is 3 4 5. Y is not

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