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Mathematics 5 Online
OpenStudy (anonymous):

I have a math question if anybody can help :)!! thnx

OpenStudy (anonymous):

A ladder leans against a house at a 60° angle to the ground. If the ladder extends to a length of 158 inches, what is the height of the house rounded to the nearest hundredth of an inch? Type the numeric answer only in the box below.

OpenStudy (zehanz):

You could use this property of the 30-60-90 triangle: Its sides have proportions \(a : a \sqrt{3} : 2a\), going from the shortes to the longest.

OpenStudy (anonymous):

okay but how would I plug that in??

OpenStudy (anonymous):

use the sine formula sin(theta) = opposite side/ hypotenuse. in your case theta is 60 degrees the opposite side is x what is the hypotenuse.

OpenStudy (anonymous):

ummmm....158?

OpenStudy (zehanz):

You can plug it in this way: FG = 158 = 2a, so a = 79 (=EF) The height of the house is x = 79√3. Calculator says: 136.83 inches.

OpenStudy (anonymous):

okay...a little confused..but thank you for your help :)

OpenStudy (zehanz):

YW! Here is a drawing of this 30-60-90 triangle, together with the proportions.

OpenStudy (anonymous):

thank you so much!!

OpenStudy (zehanz):

Important thing to remember here is: if you have the 30-60-90 triangle, you only need ONE side to be able to work out the other two sides.

OpenStudy (anonymous):

OKAY I will remember that :) thank you!!

OpenStudy (zehanz):

Reason for a and 2a is simple: you can consider the 30-60-90 triangle as a half equilateral triangle. The a√3 follows from good old Pythagoras.

OpenStudy (anonymous):

okay thanks again :) and you have a good day (:

OpenStudy (zehanz):

YW! I'll stop now :D

OpenStudy (anonymous):

haha lol :) you were helpful!!

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