A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • 4 years ago

Suppose θ is in the interval (180°, 225°). Find the sign of each function value. a) Cos(2θ) b) tan(θ-90°) c) sin(θ/2)

  • This Question is Closed
  1. dumbcow
    • 4 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    a) 2A puts you in 1st quadrant --> cos(2A) is positive b) A-90 puts you in 2nd quadrant --> tan(A-90) is negative c) A/2 puts you in 2nd quadrant --> sin(A/2) is positive

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

    How do you get to that? Is there any mathmatics behind it that will help me associate it so I can repeat this?

  3. anonymous
    • 4 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    this (rough) diagram should help\ |dw:1328624954731:dw|

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

    so in first quadrant (0-90) all trig ratios are positive in 2nd (90-180) sine is pos. cos and tan are neg. in 3rd (180-270) tan is pos. sin and cos are neg. in 4th (270-360) cos is pos. sin and tan are neg.

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

    also as an aid to memory you can memorise CAST - 'Cos - All - Sin - Tan' these are the ratios which are positive in the quadrants : |dw:1328625567936:dw| eg 250 degrees - is in third quadrant :- the tangent is positive, cos and sine are negative

  6. anonymous
    • 4 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hope this helps

  7. anonymous
    • 4 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yes this is great information. However, I still don't understand how you find: Suppose θ is in the interval (180°, 225°). Find the sign of each function value. a) Cos(2θ) : What would this be Cos(2*180)? b) tan(θ-90°) c) sin(θ/2)

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

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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.