cosines

  1. J

    Law of Cosines

    Navigation. Airport B is 300 mi from airport A at a bearing N 50 degree E. A pilot wishing to fly from A to B mistakenly flies due east at 200 mi/h for 30 minutes, when he notices his error. a. How far is the pilot from his destination at the time he notices the error? b. What bearing should...
  2. T

    law of sines and law of cosines

    how do you know which one to use?
  3. N

    Help - Sum of Cosines

    I need help with the sum of cosines. Specifically this problem: Cos(2pi/3 + pi/4) Detail is highly appreciated. Thank you in advance.
  4. K

    Need help with solving sums of cosines

    Hi all, I would appreciate any help with this problem. Thanks for your time, How do I algebraically (or similarly) solve any equation in the form of: cos(a) + cos(b) + cos(c) + cos(d) = 0 a, b, c, and d are all functions of x (Assuming that a, b, c, and d are chosen so that a solution exists)...
  5. J

    more precalc.. law of sines and cosines

    this is hard to explain without a diagram.. but ill try: a plane is traveling 30 degrees NE at 400 mph the wind is traveling 60 degrees NE at 34 mph what is the new speed of the plane and its bearing (because of the effect of the wind)? can you explain too? thanks!
  6. J

    precalc help (law of sines and cosines)

    hard to explain without a diagram, but: a point on the ground is 200 feet from a water tower the angle of elevation to the top of the tower is 18 degrees the angle of elevation to the bottom of the tower is 15 degrees how tall is the water tower? (i think the water tower is on a hill?) thanks!
  7. C

    Need help inputting law of cosines on ti83+

    Solve: Ok, so I use the law of cosines, correct? cos A = b^2+c^2-a^2/2bc Now, when I input this into my ti83+: 2017^2+2938^2-2506^2/2(2017x2938) I get -1.86075644e13 So, next I am supposed to multiply by the inverse cosine, right? But -1.8 is obviously not right...
  8. A

    Law of Cosines, help!

    Given these dimensions, I have to find the remaining angles. I know you're supposed to use the law of cosines which would be a²=b²+c²-2bcCosA So plugging that in I have a²=2337²+5168²-2(2337(5168))CosA Is this correct? I'm not sure how to get rid of the CosA.
  9. B

    Help with inverses of cosines

    Find the exact value of the expression, if it is defined. (If it is not defined, enter NONE.) So this is my problem. Ive tried what makes sense pi/5, negative pi/5, and undefined, which isnt any of them! I know its something simple i'm missing!
  10. Q

    sum of cosines

    I have the function: y(t) = (cos(300πt) + sin(500πt))^3 I need too expand the expression of y to get a sum of cosines with positive frequencies. Using trigonometric identities find the frequencies of resulting sine waves.Can someone help me with that? Thank you
  11. lmschneider

    Law of Sines and Cosines

    Solve triangle by either Law of Cosines or Law of Sines. 1. b = 7 c = 5 angle C = 150 2. c = 12 angle A = 140 angle C = 20 3. a = 22.3 b = 16.1 angle B = 100 4. A ship sails due west from a harbor for 22 nautical miles. It then sails 62 degrees south of west for another 15 miles...
  12. P

    laws of cosines

    Okay I am FLIPPING OUT. I have a math test tomorrow. I have to go to bed in an hour, and I just now learned that I have to be able to derive three separate things! Please help me. I am seriously distressed. 1. How do I derive the Law of Cosines, vector style? Okay here's what I have...the...
  13. N

    tetrahedron, Isosceles, law of cosines

    regular tetrahedron with base ABCD has a point in its interior we call P such that, AP=BP=sqrt(11) CP=DP=sqrt(17) AB=BC=CD=AD=x what is the value of x? I have tried: if we let theta be <APB, phi be <APD, and omega be <PCD we have using law of cosines (i)x^2 =2*11-2(11)cos(theta) (ii)x^2...
  14. L

    Calculating partial derivatives by implicit differentiation of the Law of Cosines

    If a,b,c are sides of a triangle and A,B,C are the opposite angles, calculate бA/бa, бA/бb, бA/бc by implicit differentiation of the Law of Cosines. Any help would be appreciated!
  15. G

    Word problem has to do with law of cosines

    In major league baseball, the four bases form a square whose sides are each 90 feet long. The front edge of the pitching rubber on which the pitcher stands is 60.5 feet from home plate. a) Find the distance from the center of the front edge of the pitching rubber to first base. b) Find the...
  16. M

    Law of Cosines

    Use the Law of Cosines to prove the identity (cosA/a) + (cosB/b) + (cosY/c) = (a^2 + b^2 + c^2)/(2abc
  17. M

    Law of Sines, Cosines and Tangents

    What is the basic difference between the Law of Sines, Law of Cosines and Law of Tangents? When do we use one and not the others?
  18. T

    Law of Cosines

    I dont know how to find the side! Problem: a= 16 c= 12 B= 63degrees I know the formula to use afterwards. a^2=b^2 + c^2 - 2bc COS A
  19. K

    The law of cosines

    round each angle measures to the nearest degree and side measures to the nearest tenth. Triangle ABC, a = 15, b = 19, c = 28 i dont understand what formula to use for this geometry problem and how to set it up to work it out to get the answer
  20. sjcomp

    Period of the sum of two cosines

    Hello, I remember that if I sum two cosine waves the period of the resulting function will be extended. How do I find this new period? I also remember that if the ratio of the periods satisfies a condition then the period never repeats. I do not remember what the condition is. Or maybe it...