Hi welcome to MooMooMath. Today we are going to look at sector area. The best way to explain sector area is to think of it as a pizza slice. So if I have a circle and take out a slice of it, that what I call sector area. OK we need to know a couple of pieces of information to plug into our area formula. We need to know the radius and the measure of the arc. The measure of the arc is equivalent to the central angle. Since this is a 90 degree angle this means the arc angle is also 90 degrees. Now let’s put it into our formula. Let me explain the formula. The measure over 360. Notice if I put 90 over 360, I will reduce that to one fourth of the circle. As you can see 90 degrees is one fourth of the circle. Then I will multiple this by the area which is pi R squared. If I know the whole area of the circle and divide into fourths I will know the area of just this slice. So the area of the circle is pi times my radius, my radius is 8 so 8 squared is 64 so I will take one fourth times pi times 64 and one fourth of 64 is 16 pi You can leave your answer like that or you can multiple it out. So 16 times 3.14 which is 50.4 and it is always the units squared. Let me pop up the rules for area sector. The area of a sector is like a pizza slice you find the area of a circle times the fraction of the circle that you are finding. Hope this video helpful.

Take the measure of the central angle and divide by360