Question 164005
 Prove that the area of a circular sector of radius r with central angle theta is , where theta is measured in radians. 
The following is what I've come up with so far, am I on the right track? 
I can tell that a circular sector looks similar to a triangle with an arc replacing its flat base. The area of a triangle is computed using A=1/2bh. Therefore: 
h=r
b=s=r(theta) 
A=(1/2)rr(theta) which is simplified to {{{A=(1/2)r^2}}}
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{{{A=(1/2)r^2*theta}}}  (You left out the theta)
What you've done is the correct approach.  This can be done as a limit, or by integral calculus, which is essentially the same thing.  I don't know if your instructor would accept an integration, tho, it depends on the level of your class.