Proving circles are similar

Which of these best describes π?

• The ratio of the circumference of a circle to its diameter.

• The square root of the area of a circle.

• The radius of a circle times 3.14.

• The ratio of the radius of a circle to its diameter.

Which of the following formulas do we use to find the Circumference of a circle when given the diameter?

• C = πd

• A = πr²

• C = 2πr

• A = πr²

Which of the following formulas do we use to find the Circumference of a circle when given the radius?

• C = πd

• A = πr²

• C = 2πr

• A = πr²

Identify the center and radius of the circle.

• center: (1, -2); radius: 5

• center: (-2, 1); radius: 5

• center: (-2, 1); radius: 10

• center: (1, -2); radius: 10

To show that all circles are similar, you would need to dilate the preimage (F) and the translate it until you match the image (F'). What is the value of the scale factor, k?

• 1/4

• 1/2

• 1

• 4

To show that all circles are similar, you would need to dilate the preimage (F) and the translate it until you match the image (F'). Select the correct translation rule.

• (x, y) --> (x + 9, y + 4)

• (x, y) --> (x - 9, y - 4)

• (x, y) --> (x + 4, y + 9)

• (x, y ) --> (x - 4, y - 9)

To show that all circles are similar, you would need to dilate the preimage (F) and the translate it until you match the image (F'). What is the scale factor, k?

• 1/4

• 1/2

• 2

• 4

To show that all circles are similar, you would need to dilate the preimage (F) and the translate it until you match the image (F'). Select the correct translation rule.

• (x, y) --> (x + 2, y + 8)

• (x, y) --> (x - 2, y - 8)

• (x, y) --> (x + 8, y + 2)

• (x, y) --> (x - 8, y - 2)

Are the parts of the circle similar? r = 10, c = 40, r’ = 5, c’ = 40

• Yes, because the ratios are proportional.

• Yes, because the c’s are the same.

• No, because parts of the circle are congruent.

• No, because the ratios are not proportional.

If r = 10, c = 15, r’ = 6, find c’.

• 9

• 90

• 4

• 0.11