Geometry: circles

Pi, radians, circumference Links: khan academy on radians

5 flashcards · Mathematics · by lakesare

1. What is Pi physically?

   circumference of half a circle / its radius = 3.14...

2. How can we describe a relationship between arc BC and angle A?

   Arc BC subtends angle A.

3. What is 1 radian physically?

   When you have a circle, and an arc of the length of one radius, the subtended angle will be 1 radian.

4. Considering the definition of a radian, - how many radians would the whole circle circumference subtend?

   Circle circumference length = 2 * Pi * radius as we know (that's just a nature of circles). Therefore angle subtended by circumference = amount_of_radiuses radians = 2 * Pi radians.

5. Find area of the sector OAB if you know angle θ radius r