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Mathematics 7 Online
OpenStudy (anonymous):

i need help ill just put the pic in the comment

OpenStudy (anonymous):

OpenStudy (mathstudent55):

This problem deals with a 30-60-90 triangle.

OpenStudy (mathstudent55):

|dw:1408506104030:dw|

OpenStudy (mathstudent55):

Are you familiar with the famous 30-60-90 triangle?

OpenStudy (anonymous):

not really, hope i don't seem dumb for asking, its cuz i got placed into advanced math and i have to figure this whole book out till summer ends so sorry

OpenStudy (anonymous):

no

OpenStudy (mathstudent55):

Don't be sorry. You want to learn math. That's great. I'll help you.

OpenStudy (mathstudent55):

There are two famous right triangles that are used often in math. For both of these triangles, the ratios of the lengths of the sides are known. One such triangle is the 45-45-90 triangle. The other one is the 30-60-90 triangle.

OpenStudy (mathstudent55):

Let's go over the 30-60-90 triangle since this is what your problem deals with.

OpenStudy (mathstudent55):

The name "30-60-90 triangle" comes from the measures of the angles. A 30-60-90 triangle has angles measuring 30 degrees, 60 degrees, and 90 degrees. Because of the 90-degree angle, which is a right angle, the 30-60-90 triangle is a right triangle.

OpenStudy (mathstudent55):

Here is a 30-60-90 triangle. |dw:1408506553825:dw|

OpenStudy (mathstudent55):

The ratio of the lengths of the sides of a 30-60-90 triangle is: \(a : b : c = 1 : \sqrt 3 : 2\)

OpenStudy (mathstudent55):

Notice that \(a\) is the smallest side. It is opposite the smallest angle, 30 degrees. \(a\) is the small leg. \(b\) is the large leg. It is opposite the 60-degree angle. \(c\) is the hypotenuse and the longest side of the triangle. It is opposite the 90-degree angle.

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

i understand

OpenStudy (mathstudent55):

From the ratio, you see that the hypotenuse is twice the length of the short leg. Also, you see that the long leg is \(\sqrt 3\) times longer than the short leg.

OpenStudy (mathstudent55):

Now let's look at your problem.

OpenStudy (mathstudent55):

You are given the length of the hypotenuse. You are asked for the length of the long leg.

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

Use this statement first: "From the ratio, you see that the hypotenuse is twice the length of the short leg." Since the hypotenuse has length 24, what is the length of the SHORT leg?

OpenStudy (anonymous):

12?

OpenStudy (anonymous):

?

OpenStudy (mathstudent55):

Correct. The short leg measures 12. Now we use the second statement: "Also, you see that the long leg is \(\sqrt 3\) times longer than the short leg." The short leg measures 12. The long leg is \(\sqrt 3\) times longer than the short leg. What is the length of the long leg?

OpenStudy (anonymous):

why do u put the square root sign

OpenStudy (anonymous):

cuz w/o sign if it was 3 x more then it would be 36

OpenStudy (mathstudent55):

But it isn't 3 times longer. It is sqrt(3) times longer.

OpenStudy (anonymous):

uh

OpenStudy (anonymous):

how do u calculate that?

OpenStudy (anonymous):

square root of 3 times longer of 12

OpenStudy (mathstudent55):

I can show you how the ratios of the sides of the 30-60-90 triangle can be calculated.

OpenStudy (mathstudent55):

Here's an equilateral triangle. All sides have a length of 2. |dw:1408507986086:dw|

OpenStudy (mathstudent55):

What are the angle measures of an equilateral triangle?

OpenStudy (anonymous):

uhm 60

OpenStudy (mathstudent55):

Great. Now we have this info on this triangle: |dw:1408508268154:dw| So far so good?

OpenStudy (anonymous):

yup

OpenStudy (mathstudent55):

Now we drop an altitude from the top vertex to the bottom side. (Remember, an altitude is perpendicular to the opposite side.) |dw:1408508376594:dw|

OpenStudy (mathstudent55):

|dw:1408508507534:dw|

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