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    I can't see how this is possible to do?, I can't do any of the parts
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    (i)60²=b²+c²-2bc cosA
    =50²+c²-2(50)(c)cos150
    3600-2500=c²+100c cos150
    c²+50c-1100=0
    Solve quadratic

    c=(-50√3±√(2500(3)+4400))/2=(-50√3±√11900)/2=-25√3±√2975
    If minus, c is negative, which is not possible, so must be plus
    c=11.2m (3sf)

    By motorway: time=(11.2+50)/3=20.4time units (3sf)
    non-motorway: time=60/2=30time units.
    Quicker by motorway
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    cheers make sense now, can you try the other two parts please
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    (ii)(50+40)/3=30time units
    distance a=30*2=60
    60²=40²+50²-2(40)(50)cosA
    3600-1600-2500=-8000cosA
    5/80=cosA
    A=86.4°
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    (iii)time=2x/3
    distance a=(2x/3)(2)=4x/3
    (4x/3)²=2x²-2x²cosA
    (16x²/9) - 2x²=2x²/9=-2x²cosA
    cosA=2x²/(9*(-2x²))=-1/9
 
 
 
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