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    Given that angle A is reflex and cosA = root13 / 7
    (a) find the exact value of sinA
    (b) find the exact value of tanA

    I generally understand the question but I need someone to explain the angles and signs to me. If angle A is in quadrant 3 then shouldn't cosA= - root13/7?
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    (Original post by Anon736)
    Given that angle A is reflex and cosA = root13 / 7
    (a) find the exact value of sinA
    (b) find the exact value of tanA

    I generally understand the question but I need someone to explain the angles and signs to me. If angle A is in quadrant 3 then shouldn't cosA= - root13/7?
    It'll be in the 4th quadrant surely?
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    (Original post by Anon736)
    Given that angle A is reflex and cosA = root13 / 7
    (a) find the exact value of sinA
    (b) find the exact value of tanA

    I generally understand the question but I need someone to explain the angles and signs to me. If angle A is in quadrant 3 then shouldn't cosA= - root13/7?
    Reflex angles are greater than 180 degrees, but are also less than 360 degrees so A could be in the fourth quadrant, making it positive.
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    (Original post by NiamhM1801)
    It'll be in the 4th quadrant surely?
    Well actually thats a good question because a reflex is greater than 180 so I actually don't know if its quadrant 3 or 4.
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    (Original post by Anon736)
    Given that angle A is reflex and cosA = root13 / 7
    (a) find the exact value of sinA
    (b) find the exact value of tanA

    I generally understand the question but I need someone to explain the angles and signs to me. If angle A is in quadrant 3 then shouldn't cosA= - root13/7?
    Reflex angle covers both 3rd and 4th quadrant since refle angle is angle bigger than π. So this tells you that in fact angle A is in fact in the 4th quadrant. So sinA will be negative and so will tanA - just sketch the graphs and you will see this.
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    (Original post by h3rmit)
    Reflex angles are greater than 180 degrees, but are also less than 360 degrees so A could be in the fourth quadrant, making it positive.
    For a question like this how do you know which one to use?
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    (Original post by Anon736)
    For a question like this how do you know which one to use?
    cosA is positive, therefore it has to be in the 4th. Remember the diagram
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    (Original post by B_9710)
    Reflex angle covers both 3rd and 4th quadrant since refle angle is angle bigger than π. So this tells you that in fact angle A is in fact in the 4th quadrant. So sinA will be negative and so will tanA - just sketch the graphs and you will see this.
    But why can it not be in the 3rd quadrant?
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    (Original post by NiamhM1801)
    cosA is positive, therefore it has to be in the 4th. Remember the diagram
    ahhhhhhh
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    Thanks for the help you guys
 
 
 
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