Similar Triangles and Why it helps with Trig Ratios

Complete the sentence:

This is an

You can get the scale factor if you use: (choose 2)

• Count the side of the new square and divide by the count of the original square

• Choose one point and it's dilation, divide the dilated x (or y) value by the original value's x (or y) value.

• Count the side of the original square and divide by the count of the new square

• Choose one point and it's dilation, divide the original x (or y) value by the dilated value's x (or y) value.

You look at an ant under a magnifying glass.

What is the ​ (a)   of the ant if...

The ​ (b)   of the ant is ​ (c)   the​ (d)  

and the actual length is ​ (e)   cm?

• actual length
• image
• 8 times
• 5.2
• actual size

When you look at an ant under a magnifying glass... find the actual length of the ant if the image of the ant is 8 times the actual size and the ant has a length of 5.2 cm.

Plug the facts into the graphic organizer.

a

b

c

d

Actual

Magnified Image

Scale Factor

Ant

After figuring out the scale factor for UV to U'V',

Find the values for V'W' AND U'W'

b

c

d

e

a

And again, same

105

77

7

Same as Scale factor above

How do I know ABE is similar to DBC?

c

d

e

b

a

:( Left Vertical

Alternate interior bottom

Alternate Interior Top

Thus, Similar by AA

:) Right Vertical

A 12 foot vertical post casts a 54 inch shadow.

A cell phone tower casts a 200 foot shadow

How tall is the cell phone tower in feet?

a

b

c

d

4.5 feet

12 foot

x

200 foot

A 12 foot vertical post casts a 54 inch shadow.

A cell phone tower casts a 200 foot shadow

How tall is the cell phone tower in feet?

After I ​ (a)   12 times ​ (b)   and divide by ​ (c)   ,

That will make the cell phone tower ​ (d)  

• 533.3 feet.
• cross multiply
• 200
• 4.5

Are you going to do the Extra Credit on finding the missing side?

• Yes

• No

How do you solve the for the missing leg of a right triangle when you have only the right angle and 2 of the sides?

• You use the sin trig ratio.

• You use the cos trig ratio.

• You use the tan trig ratio.

• You use Pythagorean theorem.