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eroshea
Group Title
The axis of the cone 2m long makes an angle of 65 degrees with its horizontal base. What is the area of the base if its volume is 5 cu. m?
 one year ago
 one year ago
eroshea Group Title
The axis of the cone 2m long makes an angle of 65 degrees with its horizontal base. What is the area of the base if its volume is 5 cu. m?
 one year ago
 one year ago

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agent0smith Group TitleBest ResponseYou've already chosen the best response.1
dw:1355654103593:dw Guessing it looks like this...
 one year ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
but it is not a right triangle so i can't use SOH CAH TOA there
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
You still can. Notice the height h makes a right angle with the base. dw:1355654861209:dw Volume of a cone is 1/3x(area of base)x(height) or \[V = \frac{ 1 }{ 3 } B h\] B is area of the base, h is height. We can find height from the diagram: \[\sin 65 = \frac{ h }{2 }\] so h=2sin65 and we know V = 5 cm^3 \[5 = \frac{ 1 }{ 3 } B \times 2 \sin 65\]
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
This diagram may help: http://upload.wikimedia.org/wikipedia/commons/d/d2/Cone_3d.png notice the cone on the right, h makes a right angle with the base, and we know the angle that the axis makes with the base.
 one year ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
B is 8.28 and B = pi r^2 root 8.28/pi = r ??? is that correct?
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
Remember that the question is asking for the area of the base, which is the B. It's not asking for the radius.
 one year ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
yes.. but i'm just asking whether what i did up there is right or wrong..
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
I got B as 8.275 m^2, so you're correct. Don't forget the units, metres squared. btw i made a mistake up there, i said V = 5 cm^3 but it's m^3 not cm^3.
 one year ago

eroshea Group TitleBest ResponseYou've already chosen the best response.1
that's fine.. thanks for helping :))
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
If you were asked for the radius, then you'd do as you did: \[r = \sqrt{\frac{ 8.275 }{ \pi }}\]
 one year ago
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