What is the area formula for a half circle?

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Answer 1 · 2015-12-25T02:47:51

#(pir^2)/2#

The typical area for a circle is:

#color(white)(sss)A=pir^2#

Divide both sides by #2#, or multiply both by #1/2#, to find the formula for half the area:

#color(white)(sss)A/2=(pir^2)/2#

We can do a practice problem: what's the area of a half a circle (a semicircle) with a radius of #6#?

#color(white)(sss)A_"semicircle"=(pi(6)^2)/2#

#color(white)(sss)=>(36pi)/2#

#color(white)(sss)=>18pi#