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    Siustrulka's Avatar
    Siustrulka Posts: 33, Reputation: 1
    Junior Member
     
    #1

    Jan 11, 2008, 12:45 AM
    Solving Trigonometric Equations
    I am totally lost with this

    solve:
    2cos^2x=sinx+1

    tan^2x=3tanx

    verify identity:

    1-cot^4x=2csc^2x-csc^4x
    SirOracle's Avatar
    SirOracle Posts: 11, Reputation: 1
    New Member
     
    #2

    Jan 11, 2008, 01:24 AM
    2cos^2(x) = sin(x) + 1
    2(1 - sin^2(x)) = sin(x) + 1
    2 - 2sin^2(x) = sin(x) + 1
    0 = 2sin^2(x) + sin(x) - 1
    0 = (2sin(x) - 1)(sin(x) + 1)
    2sin(x) - 1 = 0 sin(x) + 1 = 0
    2sin(x) = 1 sin(x) = -1
    sin(x) = 1/2 x = 3pi/2
    x = pi/6, 5pi/6

    tan^2(x) = 3tan(x)
    tan^2(x) - 3tan(x) = 0
    tan(x)(tan(x) - 3) = 0
    tan(x) = 0 tan(x) - 3 = 0
    x = 0, pi tan(x) = 3
    x = tan^-1(3)

    1 - cot^4(x) = 2csc^2(x) - csc^4(x)
    (1 - cot^2(x))(1 + cot^2(x)) = 2csc^2(x) - csc^4(x)
    (1 - cot^2(x))(csc^2(x)) = 2csc^2(x) - csc^4(x)
    ([sin^2(x) / sin^2(x)] - [cos^2(x) / sin^2(x)])(csc^2(x)) = 2csc^2(x) - csc^4(x)
    (sin^2(x) - cos^2(x))(csc^4(x)) = 2csc^2(x) - csc^4(x)
    (sin^2(x) - [1 - sin^2(x)])(csc^4(x)) = 2csc^2(x) - csc^4(x)
    (2sin^2(x) - 1)(csc^4(x)) = 2csc^2(x) - csc^4(x)
    2csc^2(x) - csc^4(x) = 2csc^2(x) - csc^4(x)

    I hope that all makes sense and that I did not use too many parentheses... there needs to be a more readable way to type equations.
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
    Ultra Member
     
    #3

    Jan 11, 2008, 01:39 PM
    ..
    .there needs to be a more readable way to type equations.
    There is, it's called LaTex and this site implements it. Like so:




    Click on quote to see the code I used to get that display.
    chamansh02's Avatar
    chamansh02 Posts: 1, Reputation: 1
    New Member
     
    #4

    Jan 15, 2010, 04:10 AM
    prove that: cos^A=m^-1/n^-1,when sinA=msinA & tanA=ntanA

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