Thread: Arc Length, and Area of a sector

Hi i need soem help on doign a problem please! I actually asked this problem to the teacher and showed him my work if this was how to do the problem and he said yes its all correct so i input it in the computer at home and it said the answer was wrong! here is the problem.


An arc of length 3 feet is cut off by a central angle of π/2 radians. Find the area of the sector formed. (Round the answer to two decimal places.)

answer goes
|
V
______ ft^2



So what i did was. since they gave me s=3 and r=pi/2 i did 3/(pi/2), and i get 1.909859317. and then this gives me theta. so then i put it in the 1/2(r)^2(theta) and get 2.35619449 then round that to 2.36 and it says im wrong o_0 help please! thxs!

Originally Posted by Nismo

Hi i need soem help on doign a problem please! I actually asked this problem to the teacher and showed him my work if this was how to do the problem and he said yes its all correct so i input it in the computer at home and it said the answer was wrong! here is the problem.


An arc of length 3 feet is cut off by a central angle of π/2 radians. Find the area of the sector formed. (Round the answer to two decimal places.)

answer goes
|
V
______ ft^2



So what i did was. since they gave me s=3 and r=pi/2 i did 3/(pi/2), and i get 1.909859317. and then this gives me theta. so then i put it in the 1/2(r)^2(theta) and get 2.35619449 then round that to 2.36 and it says im wrong o_0 help please! thxs!

how did u get 36/pi?

Originally Posted by Nismo

how did u get 36/pi?

first of all it was , which is .





so ... what is ?

Originally Posted by Nismo

Hi i need soem help on doign a problem please! I actually asked this problem to the teacher and showed him my work if this was how to do the problem and he said yes its all correct so i input it in the computer at home and it said the answer was wrong! here is the problem.


An arc of length 3 feet is cut off by a central angle of π/2 radians. Find the area of the sector formed. (Round the answer to two decimal places.)

answer goes
|
V
______ ft^2



So what i did was. since they gave me s=3 and r=pi/2 i did 3/(pi/2), and i get 1.909859317. and then this gives me theta. so then i put it in the 1/2(r)^2(theta) and get 2.35619449 then round that to 2.36 and it says im wrong o_0 help please! thxs!

I must confess that the last paragraph mystifies me. How does one "do" 3/(pi/2)? What do "s" and "r" represent and why did you divide s by r?

Do you know that pi/2 (90 degrees) is 1/4 of a complete circle? Do you know that the circumference of a circle is 2pi r (r is the radius of the circle). Here you know that 1/4 of the circle has circumference 3, what is the circumference of the entire circle? What is the radius of that circle?

Do you know that the area of a circle is pi r^2? What would the area of a circle of this radius be? What is the area of 1/4 of that circle?

Originally Posted by HallsofIvy

I must confess that the last paragraph mystifies me. How does one "do" 3/(pi/2)? What do "s" and "r" represent and why did you divide s by r?

Do you know that pi/2 (90 degrees) is 1/4 of a complete circle? Do you know that the circumference of a circle is 2pi r (r is the radius of the circle). Here you know that 1/4 of the circle has circumference 3, what is the circumference of the entire circle? What is the radius of that circle?

Do you know that the area of a circle is pi r^2? What would the area of a circle of this radius be? What is the area of 1/4 of that circle?

well this was my thinking. Since i know a= 1/2r^2theta. then since i was given radius omg -_- nvm i keep getting the radius and radian r mixed up..... but yeah ill keep going on though.. sincei thought they already gave me radius i was going to find theta so used the s=r*theta and then that got me theta and i pluged that in and wahla -_- but yeah r=radius not radian....