Geometry - Area and circumferences of a circle.

What do you use to find the radius and diameter if given the circumference?

C=πd

What to use to find area when given the circumference?

C=πd

What to use to find radius and diameter when given area?

A=πr2

What to use to find circumference when given area?

A=πr2

What is this?

Radius, and it’s half of the diameter.

What is this?

Diameter, and it’s twice as much as the radius.

What is this?

A chord. Anything inside the circle that connects to another letter. For this one it’d be AB with a line above it. —

What is this?

A secant. It’d be labeled as AB, but instead of a line above it. It’s a line with arrows going outward each side. ←→

What is this?

Tangent. It’ll be labeled as LP with a line above it like this ←-→. If there were three letters, and it was N below the P. It’d be LN.

Where is the point of tangency?

The point of tangency would be P. The point of tangency is always the one that touches the circle. The point in the middle of the line tangent.

Example problems

What’s the secant of this circle?

It’s necessary for the line to have arrows going outward if they’re either secant or tangent.

What is the tangent of the circle?

Match the part of the circle with the term that best describes it.

Check your answers.

Name the term that best describes the given line, segment, or point.

Look back at the slides for help, and solve.

Look back at the slides if you need help, and solve.

Look back at the slides if you need help, and solve.

Find the area and circumference.

Find the area and circumference.

Remember these two formulas. C=πd and A=πr2.

Also, remember if you’re labeling a pair. If they’re secant or tangent, put a line with outward arrows above the pair. But if they’re not secant or tangent, just a line above the pair.