Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

samnatha

  • 2 years ago

find the values of b for which the line 5x + by = 169 is a tangent to x^2 + y^2 =169... please help

  • This Question is Closed
  1. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    well, the b is part of slope for the line, and a derivative is the slope of an equation .... can you do a derivative?

  2. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i don't think so

  3. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    hmm, what methods have you been working with then? circles dont need calculus, but it does tend to be useful

  4. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1354822242160:dw| im sure calculus would make it easier by far; are you in calculus and just learning derivatives by chance?

  5. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well this is under the geometry chapter

  6. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    hmm well, the y intercept of the line would need to be greater that 14 to at least have shot at being tangent to the circle 169/b > 14; 169/14 > b ... 14 > b

  7. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    the slope of the line itself is -5/b; which means that the slope would be -5/14 or smaller

  8. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well the way we have been doing it is we get the radius and then use the distance formula ?

  9. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    that does sound like something more doable to me :) radius is sqrt(169) = 14 and the slope of the radius would have to be b/5 to be perp to the line

  10. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    is the radius not 13 ?

  11. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    lol .... fine, if you wanna be "correct" and all. 12: 144 13: 169 yeah it is ... i tend to get it mixed around with the 14 14: 196

  12. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ah its fine i did in the calculator haha

  13. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    line of the radius would have to be: y = b/5 x line of the tangent is given as: y = -5/b x + 169/b any way to compare the 2?

  14. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    divide by b ?

  15. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    y' = -n/m for any point (n,.m) on the circle y = -n/m (x-n) + m would be the tangent line of the circle and this has to equal the given line, with the same point (n.m) 5n +bm = 169 \[y = -\frac{n}{m}x+\frac{n^2+m^2}{m} \] 5n +bm = 169 comparing intercepts; i would say that 5^2+b^2 = 169 b^2 = 144 b = -12 , 12 lets see if the wolf likes it :) http://www.wolframalpha.com/input/?i=x%5E2%2By%5E2%3D169%2C+5x%2B12y%3D169%2C+5x-12y%3D169

  16. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    not the way your used to seeing it, but it was the only way that made sense to me :)

  17. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok it ok thanks well the answer in the back of the book is plus or minus 12

  18. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so you are right anyway

  19. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yay!! ... i got no idea how id try to approach it using the distance and radius stuff. Either too long out of geometry or never really learnt it to begin with

  20. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    haha thanks anyway its just my teacher she like to make thing complicated

  21. amistre64
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    good luck ;)

  22. samnatha
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thanks

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

    • 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.