Results 1 to 5 of 5

Math Help - Quick Question

  1. #1
    Junior Member
    Joined
    Feb 2008
    Posts
    74

    Quick Question

    Ok im doing a problem and it includes finding the values of six trig functions...my question is if im given a angle [ 315 degrees ] and after finding the reference angle what numbers do i use? Do i use (checkmark 2 / 2 and checkmark 2 / 2??
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jun 2008
    Posts
    792
    Given: \theta = 315^{\text{o}}
    Take note that this angle is in the fourth quadrant. This means that the only the cosine/secant of this angle is positive.

    First, find the reference angle.

    \theta_{ref} = 360 - 315 = 45^{\text{o}}

    Then, write down the six trigonometric functions of the original angle:

    \sin{315} = -\sin{45}

    \cos{315} = \cos{45}

    \tan{315} = -\tan{45}

    \csc{315} = -\csc{45}

    \sec{315} = \sec{45}

    \cot{315} = -\cot{45}

    I will leave the evaluation for you.

    Extra:
    • If angle is in first quadrant, all trigonometric functions are positive
    • If angle is in second quadrant, only sine/cosecant are positive
    • If angle is in third quadrant, only tangent/cotangent are positive
    • If angle is in fourth quadrant, only cosine/secant are positive
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    Thats the part I dont quite understand. Since there was no given values besides the reference angle. wont a side be messing? or do i just do it over the x or y value?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    Jun 2008
    Posts
    792
    For angles 30, 45, and 60, you can use the special 45-45-90 and 30-60-90 triangles:
    Special right triangles - Wikipedia, the free encyclopedia

    To find the value of the trigonometric functions of these angles.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Feb 2008
    Posts
    74
    omg thank you! lol thats what I meant in the begining with the checkmark 2 i forgot to take notes on this!

    thanks for your time
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. quick question
    Posted in the Calculus Forum
    Replies: 3
    Last Post: August 23rd 2009, 09:28 PM
  2. Quick question
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 30th 2008, 05:09 PM
  3. Quick question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 13th 2008, 04:51 PM
  4. Quick Question - SPP, CPP, TSP
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: December 17th 2007, 09:49 PM
  5. Quick's quick question
    Posted in the Number Theory Forum
    Replies: 22
    Last Post: July 9th 2006, 05:38 PM

Search Tags


/mathhelpforum @mathhelpforum