Find all values of x in the interval [0, 2pi] that satisfy 2 cos x + 1 > 0.
With no parentheses.
I got:
0 \< x < (2pi / 3), (4pi / 3) < x < 2pi.
Is this correct?
Also:
Find all values of x in the interval [0, 2pi] that satisfy 2 cos x - 1 = 0.
I got (pi / 3), (5pi / 3). The answers listed in the book are the same as mine.
P.S. Is there any reason why the 1 would be added to both sides of the equation first, but the 1 not subtracted from both sides of the inequality first?
With no parentheses.
I got:
0 \< x < (2pi / 3), (4pi / 3) < x < 2pi.
Is this correct?
Also:
Find all values of x in the interval [0, 2pi] that satisfy 2 cos x - 1 = 0.
I got (pi / 3), (5pi / 3). The answers listed in the book are the same as mine.
P.S. Is there any reason why the 1 would be added to both sides of the equation first, but the 1 not subtracted from both sides of the inequality first?
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1.
2cos(x) + 1 > 0
2cos(x) > -1
cos(x) > -1/2
x > 2π/3
And
x > 4π/3
2.
2cos(x) - 1 = 0
2cos(x) = 1
cos(x) = 1/2
x = π/3
And
x = 5π/3
2cos(x) + 1 > 0
2cos(x) > -1
cos(x) > -1/2
x > 2π/3
And
x > 4π/3
2.
2cos(x) - 1 = 0
2cos(x) = 1
cos(x) = 1/2
x = π/3
And
x = 5π/3