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xRAWRRx3
Group Title
Please help :(
In the figure below, triangle TED in rectangle TBCD is equilateral. If TB = 10, to the nearest hundredth, what is the length of ED?
 2 years ago
 2 years ago
xRAWRRx3 Group Title
Please help :( In the figure below, triangle TED in rectangle TBCD is equilateral. If TB = 10, to the nearest hundredth, what is the length of ED?
 2 years ago
 2 years ago

This Question is Closed

xRAWRRx3 Group TitleBest ResponseYou've already chosen the best response.0
dw:1338703391644:dw
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
Are you familiar with any trig?
 2 years ago

xRAWRRx3 Group TitleBest ResponseYou've already chosen the best response.0
well, a little bit.
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
hmm then again, you said geometry, so let me think of a way to do it without trig
 2 years ago

xRAWRRx3 Group TitleBest ResponseYou've already chosen the best response.0
no no, you can use a bit of trig if it is simple :)
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
Step 1) Label the length of ED x. So TE = x and TD = x as well since we're dealing with an equilateral triangle dw:1338704023305:dw
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
Step 2) Cut TD in half. Label the midpoint of TD point F and draw the segment EF dw:1338704102241:dw
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
The length of TF and FD are x/2 since we've cut TD = x in half
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
FE = TB, so FE = 10
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
So we have the following dw:1338704182291:dw
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
Since we have the right triangle EFD, we can say EF^2 + FD^2 = ED^2 but we know that EF = 10, FD = x/2 and ED = x, so... 10^2 + (x/2)^2 = x^2 100 + x^2/4 = x^2 400 + x^2 = 4x^2 400 = 4x^2  x^2 400 = 3x^2 3x^2 = 400 x^2 = 400/3 x = sqrt(400/3) x = 20/sqrt(3) x = 20*sqrt(3)/3 So the exact length of ED is 20*sqrt(3)/3 units.
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
After that, use a calculator to get 20*sqrt(3)/3 = (20*1.73205)/3 = 34.641/3 = 11.547 Giving us that ED is approximately 11.547 units, which rounds to 11.55
 2 years ago

xRAWRRx3 Group TitleBest ResponseYou've already chosen the best response.0
thank you so much x) you really helped me x)
 2 years ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.1
yw
 2 years ago
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