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    I understand how to use them, but can someone clearly explain to me when to use all the different formulas in Trigonometry? (For e.g: how I can tell when to use Cosine rule)
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    (Original post by chicchoc)
    I understand how to use them, but can someone clearly explain to me when to use all the different formulas in Trigonometry? (For e.g: how I can tell when to use Cosine rule)
    Cosine rule:
    2 sides + enclosed angle to find opposite side
    All 3 sides to find an angle

    Sine rule:
    Angle and opposite side + side to find the other opposite angle
    Angle and opposite side + angle to find the other opposite side

    Sine area rule:
    To find area you need 2 sides + enclosed angle
    To find a side you need the area + a side and the enclosed angle

    In right angled triangles:
    Sine:
    To find angle you need opposite side + hypotenuse
    To find hypotenuse you need angle + opposite side
    To find opposite side you need angle + hypotenuse

    Cosine:
    To find angle you need adjacent side + hypotenuse
    To find hypotenuse you need angle + adjacent side
    To find adjacent side you need angle + hypotenuse

    Tangent:
    To find angle you need opposite side + adjacent side
    To find adjacent side you need angle + opposite side
    To find opposite side you need angle + adjacent side

    Sorry if I made a mistake or my description is bad
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    My revision guide described the trig rules quite well; I can post a photo of the explanation.
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    (Original post by Loci Pi)
    Cosine rule:
    2 sides + enclosed angle to find opposite side
    or 1 side, angle, and side opposite to the angle to find other side enclosing the angle.

    Sine rule:
    Angle and opposite side + side to find the other opposite angle
    Angle and opposite side + angle to find the other opposite side

    Sine area rule:
    To find area you need 2 sides + enclosed angle
    To find a side you need the area + a side and the enclosed angle

    In right angled triangles:
    Sine:
    To find angle you need opposite side + hypotenuse
    To find hypotenuse you need angle + opposite side
    To find opposite side you need angle + hypotenuse

    Cosine:
    To find angle you need adjacent side + hypotenuse
    To find hypotenuse you need angle + adjacent side
    To find adjacent side you need angle + hypotenuse

    Tangent:
    To find angle you need opposite side + adjacent side
    To find adjacent side you need angle + opposite side
    To find opposite side you need angle + adjacent side

    Sorry if I made a mistake or my description is bad
    Not completely correct -

    Cosine rule:
    Three sides - use to get largest angle [oppostie largest side]
    Are you sure about the seond use of cosine rule - draw a diagram as it doesn't sound correct.
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    (Original post by Muttley79)
    Not completely correct -

    Cosine rule:
    Three sides - use to get largest angle [oppostie largest side]
    Are you sure about the seond use of cosine rule - draw a diagram as it doesn't sound correct.
    You're right sorry I made a stupid mistake explaining it I will edit my comment.
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    TSR won't let me upload the photo for some reason.
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    (Original post by chicchoc)
    I understand how to use them, but can someone clearly explain to me when to use all the different formulas in Trigonometry? (For e.g: how I can tell when to use Cosine rule)
    The second post in the thread was incorrect but has now been amended.
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    I have corrected the mistake now. The rest of it is correct though.
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    Name:  sine.JPG
Views: 10
Size:  99.8 KB
    Sine rule
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    Name:  cosine rule.JPG
Views: 10
Size:  112.4 KB
    Cosine rule
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    Name:  area.JPG
Views: 11
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    Sine area rule

    You can ignore the fact that 'sine' is highlighted.
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    Name:  right angles.JPG
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    Right angled triangles
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    do you have any for c3 and c4 trig?
    Posted on the TSR App. Download from Apple or Google Play
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    (Original post by RuthieG101)
    do you have any for c3 and c4 trig?
    No, sorry. The most trig I know is C2 AS level but when I come to learning C3 and C4 diagrams like that would be useful.
 
 
 
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