Pre-calculus

posted by .

a triangular shelf is to be placed in a curio cabinet whose sides meet at an angle of 105 degrees. If the edges of the shelf along the sides measures 56 centimeters and 65 centimeters, how long is the outside edge of the shelf? Round to the nearest tenth.

Thanks for any help--I stink at word problems!

  • Pre-calculus -

    Suppose you laid the triangle down in front of you.
    What would you see?

    Would it not be a simple triangle with sides 56 and 65, and the angle contained between those two sides of 105º ?

    clearly a Cosine Law question.

    x^2 = 56^2 + 65^2 - 2(56)(65)cos 105º

    solve for x

    let me know what you got.

  • Pre-calculus -

    x=95.5 cm

  • Pre-calculus -

    no, I got 96.15

    x^2 = 56^2 + 65^2 - 2(56)(65)cos 105º
    = 3136 + 4225 - 7280(-.258819)

    notice the last term will become positive, I think you subtracted it instead.

  • Pre-calculus -

    x^2=3136+4225-(0.2588)

    x^2=3136+4225+0.2588

    x^2=7361.26

    x=85.8

  • Pre-calculus -

    No ! your forgot an entire factor.

    yours: x^2=3136+4225+0.2588
    mine: x^2 = = 3136 + 4225 - 7280(-.258819)

  • Pre-calculus -

    Try again--

    x^2=3136+4225-7280(-0.2588)

    x^2=9245.06

    x=96.2 cm

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Pre Calc

    I have no idea how to do this problem I thought you would have to do something with the diagonals but not sure... The parallel sides of a trapezoid are 4 and 10 centimeters long and the oblique sides are 8 and 12 centimeters long. …
  2. geometery

    bases are isosceles triangles with parallel sides that measure 15 centimeters and 25 centimeters. the distance between the parallel sides is 12 centimeters and the length of each of the equal sides is 13 centimeters. the height of …
  3. math

    can someone please answer these questions for me?
  4. math

    a carpenter was putting up a shelf. the shelf needed to be 87 centimeters long but the piece of wood she had was 1 meter and 28 centimeters long. her saw was 46 cm long. how much did she have to cut off the piece of wood?
  5. Math

    The ratio of corresponding sides of two similar triangles is 2:7. The sides of the smaller triangle are 16 centimeters, 22 centimeters and 28 centimeters long. What is the perimeter of the larger triangle?
  6. Algebra

    How do I answer this? Robert needs to cut four shelves from a board that is 2.5 meters long. The second shelf is 18 centimeters longer than twice the length of the first shelf. The third shelf is 12 centimeters shorter than the first
  7. Algebra

    Robert needs to cut for shelves from a board that is 2.5 m long. the second shelf is 18 cm longer than twice the length of the first shelf. the third shelf is 12 cm shorter than the first shelf. the remaining shelf is 4 cm longer than …
  8. Math

    triangle abc has sides that are 20 centimeters 38 centimeters and 50 centimeters in length . it is related to triangle cde by a scale factor of 0.5 what are the lengths of the sides of triangle CDE. I need help to figure this out. …
  9. Unknown

    Carl is asked to draw a triangle with the following specifications: -all sides have whole number lengths in centimeters -the sum of the lengths of the two shortest sides equals 9 centimeters -when the side lengths are placed in order …
  10. math

    rectangles with the perimeter of 16 centimeters and sides whose lengths a whole centimeters. Label the lengths of two adjacent sides of each rectangle.

More Similar Questions