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Math Help - need these done by tomorrow - trig

  1. #1
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    need these done by tomorrow - trig

    i accidentally posted these in the trig help forum.

    10) Give that tan = -1/7 and sin > 0, use the x-y-r method to find sin and cos.

    11) Sketch a 240 angle in standard position. Label a point on its terminal side, draw the right triangle in use, indicate the direction of opening, and give all six trig function values for 240.

    12) Sketch a 90 angle in standard position. Label a point on its terminal side and use the x-y-r method to compute the six trig function values for 90.

    13) In what quadrant(s) does terminate if sin > 0 and cos < 0?
    Q1 Q2 Q3 Q4

    14) In what quadrant(s) does terminate if tan < 0?
    Q1 Q2 Q3 Q4

    15) In what quadrant(s) does terminate if cos < 0?
    Q1 Q2 Q3 Q4

    17) Use a fundamental identity to find cos if sin = 1/5, that terminates in Q2. Show work.
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  2. #2
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    Quote Originally Posted by gabby is awesome View Post
    i accidentally posted these in the trig help forum.

    10) Give that tan = -1/7 and sin > 0, use the x-y-r method to find sin and cos.
    I guess I'll solve this one and others can solve the rest

    tan\theta<0  and  sin\theta>0 so by using CAST rule we know that this is in the second quadrant (S). tan\theta=opposite/adjacent so if you draw a triangle on the second quadrant, the length of the line parallel to the y axis is 1 unit and the length on the x axis is 7 units. You can now find hypotenuse using pythagorean theorem
     \sqrt{1^2 + 7^2} = hyp<br />
= \sqrt{50}
    then use sin\theta=opposite/hypotenuse
    cos\theta=adjacent/hypotenuse
     sin\theta= 1/\sqrt{50}
    cos\theta =7/\sqrt{50}
    You can reduce the 50 under the root if you want
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