tentukan hp : a. cos x = -½ dengan 0 ≤ x ≤ 2π b. Tan x = Tan 2π/5 dengan 0 ≤ x ≤ 2π c. 1+ 2 cos 2x =0 dengan 0 ≤ x ≤ 360

a. cosx = -1/2
    cosx = cos120°
    x = 120° + k . 360°
    x = 120°
    x = -120° + k . 360°
    x = 240°
    HP = {120°, 240°}
    HP = {2/3π, 4/3π}

b. tanx = tan2π/5
    tanx = tan72°
    x = 72° + k . 180°
    x = 72°, 252°
    HP = {72°, 252°}
    HP = {2/5π, 7/5π}

c. 1 + 2cos2x = 0
    1 + 2(2cos²x - 1) = 0
    1 + 4cos²x - 2 = 0
    4cos²x - 1 = 0
    4cos²x = 1
    2cosx = 1
    cosx = 1/2
    cosx = cos60°
    x = 60° + k . 360°
    x = 60°
    x = -60° + k . 360°
    x = 300°
    HP = {60°, 300°}

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