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    solve equation

    arctan x + arctan 2x = pi/4

    take tan of both sides and use tan(A +B) expansion
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    (Original post by s-man)
    take tan of both sides and use tan(A +B) expansion
    how do you actually solve arctan..etc equations? i know that it is the inverse function of tan..etc

    (Original post by TheWolf)
    how do you actually solve arctan..etc equations? i know that it is the inverse function of tan..etc
    give me an example i dont understand wot u mean.......if arctanX=3....then X=tan3.......
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    (Original post by s-man)
    give me an example i dont understand wot u mean.......if arctanX=3....then X=tan3.......
    ok give arccos -0.5 in radians

    (Original post by TheWolf)
    ok give arccos -0.5 in radians

    2Pi/3
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    (Original post by s-man)
    2Pi/3
    please explain

    (Original post by TheWolf)
    please explain
    u need to kno ur basic trig values i.e. cos(pi/3) =0.5 etc and work backwards, by using a cos graph if it helps
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    whered u get such a wierd question ??? .. ive done so many papers and never come across such a problem ...

    if its edexcel , usually the first part fo the question helps in solving the later ... perhaps u had to prove some identity above ....

    jus use the same identity (if any ) to solve this ... other wise ... i dont think u can solve this witout using the tan ( A+B) identity
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    (Original post by f_malik)
    solve equation

    arctan x + arctan 2x = pi/4
    wot so tan(arctanx+arctan2x)=1
    (x+2x)/(1-2x^2)=1

    so x+2x=1-2x^2
    so 2x^2+3x-1=0
    so x=(-3+/-sqrt(9+8))/4
    =-0.75+-sqrt17/4
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    (Original post by s-man)
    u need to kno ur basic trig values i.e. cos(pi/3) =0.5 etc and work backwards, by using a cos graph if it helps
    please explain
    arcos-0.5 in radians= cos^-1(-0.5) =2.09



    if u want asnwer in terms of pi:
    cos^-1(-0.5) /pi = 2/3

    so arccors-0.5=(2/3) pi
    is how i'd do it. not the best method tho.
 
 
 

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