Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

eroshea

  • 2 years ago

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?

  • This Question is Closed
  1. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1355654103593:dw| Guessing it looks like this...

  2. eroshea
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    but it is not a right triangle so i can't use SOH CAH TOA there

  3. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 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 \[5 = \frac{ 1 }{ 3 } B \times 2 \sin 65\]

  4. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 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.

  5. eroshea
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    B is 8.28 and B = pi r^2 root 8.28/pi = r ??? is that correct?

  6. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Remember that the question is asking for the area of the base, which is the B. It's not asking for the radius.

  7. eroshea
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yes.. but i'm just asking whether what i did up there is right or wrong..

  8. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 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.

  9. eroshea
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    that's fine.. thanks for helping :))

  10. agent0smith
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    If you were asked for the radius, then you'd do as you did: \[r = \sqrt{\frac{ 8.275 }{ \pi }}\]

  11. eroshea
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    thanks :)

  12. Not the answer you are looking for?
    Search for more explanations.

    Search OpenStudy
    • Attachments:

Ask your own question

Ask a Question
Find more explanations on OpenStudy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.