Trigonometery help

[Mr.Everready]

My son has a question for his homework, any one help out ?#


Right angle triangle. What is x ?
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the undemocratically unelected mod of the Scottish section

[benc]

4^2+(1+2)^2=(1+4)^2
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zxr400 - zx7r

[Mr.Everready]

[hellkat]

I hate when people put a single x on the end of their posts/texts.

Its the sort of thing you expect from a 13 year old Essex girl with too much "product" in her hair.

"I went to the shops and bought some fags x "

FUCK OFF X


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Not nearly as interesting in real life.

[The Artist]

sorry its not 5 it is 1.

the top right one is 5 in total. got mixed up lol

[Mr.Everready]

[benc]

its pythagoras therom have a look at https://en.wikipedia.org/wiki/Pythagorean_theorem it should explain it better than i can
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zxr400 - zx7r

[CptBlack]

Using pythagorus:

1.)
(4)^2 + (x+2)^2 = (x+4)^2

Expanding this out gives:

2.)
16 + (x^2 + 4*x + 4) = (x^2 + 8*x +16)

The brackets aren't necessary, just there to show where each bit comes from.

Subtract from *both sides* 16 gives:

3.)
x^2 + 4*x + 4 = x^2 + 8*x

Similarly, x^2 first then 4*x gives:

4.)
4 = (8*x - 4*x) = 4*x

finally, divide both sides by 4 to give:

5.)
x = 1


Hope this helps

[Mr.Everready]

x = 1, the upright side is definitey longer than 3.
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the undemocratically unelected mod of the Scottish section

[CptBlack]

longer than 3 what? There are no units on the diagram.

It's a more complicated (slightly) version of the 3-4-5 triangle where 5 is the longest side.
3^2 + 4^2 = 5^2
9+16=25

Therefore (x+2)=3 and (x+4)=5 Thus x=1

[Chris750]

Basically the square of the hypotenuse equals the sum of the square of the other two sides.

Therefore

hypotunuse squared = opposite squared + adjacent squared

Feed all the values in, then rearange to find x

[Chris750]

Yes, just realised that cpt black- the 3 4 5 triangle is a simpler way of doing this and probably the answer they are looking for looking at the values given

[LeeR]

Yeah, my wife says it's a 3-4-5 Pythagorean triple, (a² + b² = c²) therefore x = 1

The proof via quadratic equation is:

(x+2)² + 16 = (x+4)²

expanding as:

x² + 4x + 4 + 16 = x² + 8x + 16

cancelling out (simplifying) leaves:

4 = 4x

x = 1

apparently
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[Mr.Everready]

[carvell]

Yes - what LeeR said.

Some more steps if you need them:
4^2 + (x+2)^2 = (x+4)^2
16+x^2+4+4x = (x+4)^2
x^2+4x+20 = x^2+16+8x
4x+20 = 16+8x
4 = 4x

therefore x=1
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Yamaha TDM 850

[Omega]

Ignore the diagram, they're never to scale.

[carvell]

[MattHirst]

I'm not going to repeat whats been said as it's already been calculated.

But think yourself lucky he doesn't have to use the sine rule (fairly easy) or the cosine rule ( )
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It's all fun and games until someone gets hurt, then it's bloody hilarious!!!

[Ariel Badger]

Just wait until he is in year 4
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[CptBlack]

[MattHirst]

Well you can use the sine/cosine rule if there is a 90deg angle but you can't use trig on a triangle with no 90deg angle, as you will probably know lol.

There's no need to use anything other than trig on a simple triangle like that. It's when you are given the an included angle and only 1 side etc that you need to start using trig along with sine and/or cosine.
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It's all fun and games until someone gets hurt, then it's bloody hilarious!!!

[The Artist]

Bloody hell! BCF is a bunch of nerds lol.

It is fairly simple without involving quadratics and that question looks like it is from maybe year 6 - year 8 then I doubt the kid will be doing quadratics.

3, 4, 5 simples

[Mr.Everready]

Thanks everyone, will be dished out.

I understand the equation now, a sq + b sq = c sq I just need to get him to expand it then simplify it again...does that make sense ?

Cheers
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the undemocratically unelected mod of the Scottish section

[Skudd]

God it's years since I have done these

[CptBlack]