Help with Pythagoras Theorem?

[melias24]

Hey guys here's the question i'm doing: 

Question is, is the formula right and my working out and is the answer right? dad said it's 15 or something like that....i'm just doing it how the school taught me.

~Elias

I'm in year 9 BTW

Edited February 16, 2015 by melias24

[Deletive]

B^2 = C^2 - A^2 

C is the Hypothenous (however you spell it).

If you want a great place to learn some math try 

http://www.wadgemath.ca/81-sine-cosine-and-tangent-for-right-triangles-part-1-of-2.html#/( for that chapter )

http://www.wadgemath.ca/for any other chapters. 

 

[Fred Castellum]

Not exactly helping here since I'm not a big fan of math, but I swear I've seen threads about the Pythagoras theorem posted here at least a dozen times now lol. 

 

Maths suppose to be fun right?

[terrytek]

This is easy. I just used A^2+B^2=C^2 and then I plugged in A and C and solved for B.

[leg]

Its a 30 60 90 triangle so the ratio

is 1, radical 3, 2

so A=9

B=radical 3 *9

 

sources, already took trigonometry and got 105%

 

Edit, looked at your work, since you already got 18 and 9 you can do 18Squared - 81 or {(9squared)}

 

also: cos(30)= radical 3 / 2       so 18/2=9, 9* radical 3

[Imabigmac]

angle is 60 degrees, Triangle equals 180 degrees total, 90+30 = 120. 180-120 = 60

 

C^2 - A^2 = b^2 (square root) for the length of B. The value must be less than C(18) and greater than A(9)

 

Trigonometry is probably the most interesting, and surprisingly useful, easiest and most essential math. It is especially interesting/fun when you use it in physics. 

 

And to think hundreds of years ago someone sat in their lonely stone room, and created this technique. 

[xnoobftw]

You can try TOA CAH SOH to check your answer ~ 

[leg]

They call it SOH CAH TOA state side

Sin= opposite over hypotenuse 

cos= adjacent over hypotenuse

tan= opposite over adjacent

[Imabigmac]

Lol I dunno if they teach it that way outside SG.

I learned it in Canada, so. 

 

What is SG? 

[DIV1D3]

Erm, I don't feel like doing Maths right now, already done enough Pythagoras in my lifetime...

But seriously, you people, please just use Daum Maths Editor for Chrome, looks so much better. 

https://chrome.google.com/webstore/detail/daum-equation-editor/dinfmiceliiomokeofbocegmacmagjhe/related?utm_source=chrome-ntp-icon

 

But yeh, Opposite, Adjacent and Hypotenuse... Them things. 

[T.Vengeance]

SG is short for Singapore.

 

And no, Singapore is not part of or anywhere near China.

Lol he's from vancouver. It's literally china ok (or hong kong..) and I don't think he even mentioned China?...

[Nineshadow]

I've used it so much the values just pop up without any real calculation anymore.

 b is 9 * sqrt 3.

 

Holy shit you're in the 9th grade?

[Toddwjp]

They call it SOH CAH TOA state side

Sin= opposite over hypotenuse 

cos= adjacent over hypotenuse

tan= opposite over adjacent

 

soh cah toa,

 

sex on hard concrete always hurts the others ass,

 

now you will never forget

[DimasRMDO]

A^2+B^2=C^2

 

So B^2=C^2-A^2

[ManWithBeard1990]

You can't use the pythagoras theorem to solve that question directly: you need the length of two sides to calculate the third.

But it is possible, even easy, to calculate the length of side A:

Because it is opposite a 30 degree corner and next to a 90 degree one you can use simple trigonometry. I'm not sure which values of sines and cosines they make you learn by heart but for me they were the following: sin(30)=1/2, sin(45)=sqrt(2)/2, and sin(60)=sqrt(3)/2.

And so then a=18*sin(30)=18/2=9

Then use pythagoras theorem to calculate the other side.

Or use trigonometry again. Then you need to use cosine instead of sine.

That'd be c=18*cos(30)=18*sqrt(3)/2=9*sqrt(3)

[OnCue]

B has to be less than 18, since C is the hypotenuse

[JoaoPRSousa]

What about trigonometry?

 

It makes this so much easier.

 

sin 30 = opposite cathetus (same as A or 9 whatever) / hypotenuse <=> sin 30 = o.c/18 <=> 18 x sin 30 = o.c

[APrettyCoolWalrus]

This is a 30-60-90 triangle so the shortest leg side is x, the hypotenuse is 2x, and the leg is x√3

[780blzit]

C^2 = A^2 + B^2 

 

therefore you can do:

 

B^2 = C^2 - A^2 

 

Which gives us:

 

B^2 = 18^2 - 9^2 

 

B^2 = 243

 

B = +/- √243

 

Soooo around 15.59~