How do you determine the area of a circle? Could you give an example please?

2 answers:

7 0

To determine the area if the circle, you must know the diameter or the radius of a circle.

If you know the radius of a circle, use this as your formula. Remember: Pi (the greek symbol thingy) is equal to 3.1415. (A is equal to area of the circle and r represents the radius)
$a = \pi {r}^{2}$
If you know the diameter, just divide the diameter to get the radius then use the same equation.

AlexFokin [52]3 years ago

7 0

3.14*r^2

R stands for radius.

So if you are given that the diameter of a circle is 10 feet, we know the radius is half the diameter. So the radius is 5. So the equation is going to be 3.14*5^2 so the area would be about 78.54 feet

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COMPLETE<br> Find the value of the function for O.<br> sin(45°) = ?

geniusboy [140]

Answer: $\sqrt{2}/2$ which is Choice B

This is the same as writing $\frac{\sqrt{2}}{2}$

The second "2" is not under or inside the square root.

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Explanation:

Refer to the unit circle below. I've highlighted the angle 45 degrees and its corresponding sine value. It's the y coordinate of the point on the unit circle, for this particular angle.

Therefore, $\sin(45^{\circ}) = \frac{\sqrt{2}}{2}$

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You could alternatively draw out a 45-45-90 triangle. Let x be the leg length and the hypotenuse is 1 unit long. Solve $x^2+x^2 = 1$ for x and you should get $x = \frac{\sqrt{2}}{2}$ as the length of each leg.