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Higher Maths Homework Help?

Solve:

3cosx + 2 = 4

2sin^2x = 1

3tan2x + 4 = 1

I know that these are trig equations and that I have to use the CAST diagram but I do not know how to actually do the question. Can someone help talk me through how I would do these questions?

3 Answers

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  • Ed I
    Lv 7
    9 years ago
    Favorite Answer

    3 cos x + 2 = 4

    3 cos x = 2

    cos x = 2/3

    x ≈ 0.841, 5.442

    2 sin^2 x = 1

    sin^2 x = 1/2

    sin x = ± √2/2

    x = π/4, 3π/4, 5π/4, π/4

    3 tan 2x + 4 = 1

    3 tan 2x = -3

    tan 2x = -1

    2x = 3π/4, 5π/4, 9π/4, 13π/4

    x = 3π/8, 5π/8, 9π/8, 13π/8

  • 9 years ago

    Hi KillieTillDie7, better recall these again and again

    If sin x = sin t

    then x = npi + (-1)^n t

    And if cos x = cos t

    then x = 2npi +/- t

    In case of tangent function, if tan x = tan t

    then x = npi + t

    In all the above cases n can assume any value 0,1,2,3,4,5,6,...............................

    Now let us solve the problems given by you

    1) 3 cos x + 2 = 4

    So cos x = 2/3

    x = arc cos 2/3 = 48.2 deg

    In radian 48.2/180 * pi = 0.268 pi

    Hence x = 2npi +/- 0.268 pi

    2) sin x = 1/,/2 = sin pi/4

    So x = npi + (-1)^n pi/4

    3) tan 2x = -1

    or tan 2x = - tan pi/4 = tan (-pi/4)

    So 2x = npi + (-pi/4)

    Or x = 1/2 ( npi -pi/4) = (4n-1) *pi/8

  • 9 years ago

    * 3 cosx+2 =4

    3cosx=2

    cosx= 2/3

    shift cos

    x=48 x=360-48

    x=312

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