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Mathematics 8 Online
OpenStudy (natasha18):

If RX = 4 and XS = 9, then XT =6 6.5 √13 18

OpenStudy (natasha18):

OpenStudy (natasha18):

Please teach me how to solve these not just the answer!! Thanks!

rishavraj (rishavraj):

ook wht u need to calculate??? and u see there are two right angled triangles ...so we gonna use Pythagores theorem

OpenStudy (natasha18):

ok

rishavraj (rishavraj):

so which side length u need to calculate ?? @Natasha18

OpenStudy (natasha18):

ooh sorry the question didn't come out right

OpenStudy (natasha18):

XT doesnt = 6, 6 is just one of the options

OpenStudy (natasha18):

we want to find XT

OpenStudy (mjdennis):

OK, they are right triangles, so the Pythagorean Theorem is going to work. That's a pretty common one, do you know it?

OpenStudy (natasha18):

a^2 + b^2 = c^2

OpenStudy (mjdennis):

Yep, hang on a second. @rishavraj may I jump in? I've got a slow connection so I can't see if you are still here?

rishavraj (rishavraj):

lol for sure....was stuck on my work :P

OpenStudy (mjdennis):

@Natasha18 This is a bit trick to set up, so stop me anytime with a question. The difficulty is, we have three missing sides. And the diagram is untrustworthy.

OpenStudy (natasha18):

yeah.. they're similar triangles right?

rishavraj (rishavraj):

@Natasha18 see lemme simplify it here u got 3 right angle triangles ..... cool with it ??? triangle RST , triangle RXT and triangle XST so for traingle RST ...we have RS = 13 \[RS^2 = RT^2 + ST^2 \]

OpenStudy (natasha18):

uuummm i only see two right triangles

OpenStudy (natasha18):

TXS and TXR

rishavraj (rishavraj):

@Natasha18 wht about RST ??

OpenStudy (natasha18):

it isn't a right triangle

OpenStudy (natasha18):

wait oh nvm it is lol

rishavraj (rishavraj):

http://prntscr.com/bhm0vf

OpenStudy (mjdennis):

That little square in the corner of says that there is a right angle at <RTS. That should make RTS a right triangle. Is there something that makes you think otherwise?

OpenStudy (natasha18):

no i just wasn't looking closely enough

rishavraj (rishavraj):

so in traingle RST \[13^2 = (TS)^2 + (TR)^2\] @Natasha18 u get tht??

OpenStudy (natasha18):

yeah

OpenStudy (mjdennis):

Guys, shorter way! Shorter way! @Natasha was right about similar triangles!

OpenStudy (natasha18):

@mjdennis yeah i think i was supposed to solve it using knowledge of similar triangles

rishavraj (rishavraj):

oops my bad @Natasha18

OpenStudy (mjdennis):

dw:1466184169904:dw|

OpenStudy (natasha18):

for some reason your drawing isnt loading

OpenStudy (mjdennis):

Lost the drawing. One sec. There are three right triangles, and because XT is perpendicular to the base, all three are similar. (That line XT is an altitude, right?) So if they are similar, the sides are proportional. So, @Natasha , need you to match sides for me:

OpenStudy (mjdennis):

|dw:1466184603042:dw| Ratio RX/XT on smallest triangle is going to match what ration of sides on the medium-sized triangle TXS ?

OpenStudy (natasha18):

ok well ST = TX, TS= TR=SR , RX= SX ... is that all of them?

OpenStudy (natasha18):

TX to SX

OpenStudy (mjdennis):

Maybe I read it wrong, but I get RX~TX~RT for the short sides, XT~XS~TS for the long side and RT~TS~RS for the hypotenuses.

OpenStudy (natasha18):

ok yeah i see that... im just horrible with similar triangles

OpenStudy (mjdennis):

No, you nailed the ratio. (I was horrible once, too). So RX/XT = TX/SX TX is really XT, and you know RX and SX. Can you 'bring it home'?

OpenStudy (natasha18):

36 = tx^2 so the answer is 6

OpenStudy (mjdennis):

Brava, well done! @rishavraj was on the way to an excellent solution with a quadratic equation, too.

OpenStudy (natasha18):

well im glad i did it this way... i hate quadratic equations XD

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