# Trigonometry Help

• Jul 30th 2007, 02:28 PM
TH1
Trigonometry Help
I need help for gr 10 trigonometry since I havent done it for along time and kind of forgot what to do

A tall building casts a shadow that is 9.2m long. At the same time a 1.8m person casts a shadow that is 0.4m long. How tall is the building? Find your answer to one decimal place.
I thinks its 9.2/x = 0.4/1.8 and you would cross multiply to get 9.2 x 1.8=16.56/0.4 to get 41.4.

A ramp is designed so that is rises 20cm vertically for every 1 minute horizontally. What is the vertical height of the ramp if it has a horizontal length of 4.2m?

A tree in your yard casts a shadow that is 4.5m long. Your 1.5m tall sister casts a 1m long shadow. How tall is the tree?
4.5 x 1.5 =6.75 6.75 /1=6.75

A 7.6m tall telephone casts a 6.1m shadow. The nearby school casts a 15.8m shadow. How tall is the school to 2 decimal places?
6.1 x 15.8 = 96.38 96.38/7.6=12.68

A model of the CN tower casts a shadow that is 0.9m tall and casts a shadow that is 0.2m long.If the real CN tower casts a 123.3m shadow find the height of the tower to the nearest meter
0.9 x 123.3 = 110.97 110.97/.2 = 554.85

A conical coffee cup is 20cm tall and has a diameter of 8cm. A new cup is designed that is 4cm shorter. What will be the new cups diameter. Find your answer to one decimal place
I had no idea what to do for this one

A tree has a shadow that is 12m long. If you are 1.8m tall and cast a shadow of 1.2m, how tall is the tree.

12 x 1.2= 14.4 14.4/1.8 = 8
• Jul 30th 2007, 05:02 PM
topsquark
Quote:

Originally Posted by TH1
A tall building casts a shadow that is 9.2m long. At the same time a 1.8m person casts a shadow that is 0.4m long. How tall is the building? Find your answer to one decimal place.
I thinks its 9.2/x = 0.4/1.8 and you would cross multiply to get 9.2 x 1.8=16.56/0.4 to get 41.4.

What is "9.2 x 1.8=16.56/0.4"? How about
$\displaystyle 9.2 \cdot 1.8 = 0.4x$

$\displaystyle x = \frac{9.2 \cdot 1.8}{0.4} = 41.4$
(This is not the same thing as what you wrote. Ask anyone that grades papers.)

Otherwise what you wrote is correct. ;)

Quote:

Originally Posted by TH1
A ramp is designed so that is rises 20cm vertically for every 1 minute horizontally. What is the vertical height of the ramp if it has a horizontal length of 4.2m?

"rises 20cm vertically for every 1 minute horizontally"
What?

Quote:

Originally Posted by TH1
A tree in your yard casts a shadow that is 4.5m long. Your 1.5m tall sister casts a 1m long shadow. How tall is the tree?
4.5 x 1.5 =6.75 6.75 /1=6.75

Same comment as the first problem.

Quote:

Originally Posted by TH1
A 7.6m tall telephone casts a 6.1m shadow. The nearby school casts a 15.8m shadow. How tall is the school to 2 decimal places?
6.1 x 15.8 = 96.38 96.38/7.6=12.68

A model of the CN tower casts a shadow that is 0.9m tall and casts a shadow that is 0.2m long.If the real CN tower casts a 123.3m shadow find the height of the tower to the nearest meter
0.9 x 123.3 = 110.97 110.97/.2 = 554.85

Yup.

Quote:

Originally Posted by TH1
A conical coffee cup is 20cm tall and has a diameter of 8cm. A new cup is designed that is 4cm shorter. What will be the new cups diameter. Find your answer to one decimal place
I had no idea what to do for this one

$\displaystyle \frac{8~cm}{20~cm} = \frac{x}{16~cm}$

Quote:

Originally Posted by TH1
A tree has a shadow that is 12m long. If you are 1.8m tall and cast a shadow of 1.2m, how tall is the tree.

12 x 1.2= 14.4 14.4/1.8 = 8

Yup.

-Dan
• Jul 30th 2007, 06:10 PM
TH1
For my work I wasnt sure how to type it in but I show my work the way you did it. For the question about the ramp it rises 20cm vertically for every 1 meter horizontally
• Jul 31st 2007, 04:27 AM
topsquark
Quote:

Originally Posted by TH1
For my work I wasnt sure how to type it in but I show my work the way you did it. For the question about the ramp it rises 20cm vertically for every 1 meter horizontally

So
$\displaystyle \frac{20~cm}{1~m} = \frac{x}{4.2~m}$

-Dan
• Jul 31st 2007, 01:59 PM
TH1
Thanks for the help i forgot to post 2 questions so here they are

A park desinger placed survey posts as shown in the diagram below. Measurements were made as indicated. How wide is the pond? Find your answer to 1 decimal place. The first number is 18 the bottom one is 5 and the horizontal one is 30

I thinks its 5 x 30=150 150/18=8.3

http://img508.imageshack.us/img508/8...0002vm5.th.jpg

Explain why similar triangles cant be used to measure the height of the tree in the diagram.

http://img341.imageshack.us/img341/5...ee44wr9.th.jpg

The first triangle is 8m and 18degrees the second smaller triangle is 2m and 24degress. I dont know why the triangles cant be used.