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Area of circle?

2 Answers
Mar 8, 2018

Answer:

#A = pir^2 or pi(d/2)^2#

Explanation:

#"Area of a circle" = pir^2#

or

#"Area of a circle" = pi(d/2)^2#

Where;

#A = "Area of a circle"#

#pi = 22/7 or 3.142#

#r = "radius of a circle"#

#d = "diameter of a circle"#

Recall;

#"Diameter of a circle" = "Two radius of a circle"#

#d = 2r#

Hence; #r = d/2#

That's why the Area of a circle is also; #A = pi(d/2)^2#

Mar 8, 2018

Answer:

#Area_circ=pir^2#, where #r# is the radius of the circle;
or
#Area_circ =pi(d/2)^2#, where #d# is the diameter of the circle.

Explanation:

Other formulae are possible depending upon what information you have been given about the circle (for example, you might be given 3 points on the circumference of the circle).

However, these are the most common forms.

Note that #pi# is an irrational value, approximately equal to #3.14159# (sometimes for non-critical approximations the ratio #22/7# may be used).