Y=3-2cos^2x Y=√1-sinx -3 Y=3cos^2x-1

Question

Y=3-2cos^2x
Y=√1-sinx -3
Y=3cos^2x-1

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Amity 8 tháng 2020-10-14T11:12:58+00:00 1 Answers 100 views 0

Answers ( )

  1. `a) y = 3 – 2cos^2 x`

    Ta có:

    `-1 ≤ cos x ≤ 1`

    `<=> 0 ≤ cos^2 x ≤ 1`

    `<=> -1 ≤ -2cos² x ≤ 0`

    `<=> 2 ≤ 3 – 2cos² x ≤ 3`

    `b) y = sqrt{1 – sin x} – 3`

    Ta có:

    `-1 ≤ sin x ≤ 1`

    `<=> -1 ≤ -sin x ≤ 1`

    `<=> 0 ≤ 1 – sin x ≤ 2`

    `<=> 0 ≤ sqrt{1 – sin x} ≤ sqrt{2}`

    `<=> -3 ≤ sqrt{1 – sin x} – 3≤ sqrt{2} – 3`

    `c) y = 3cos² x – 1`

    Ta có:

    `-1 ≤ cos x ≤ 1`

    `<=> 0 ≤ cos^2 x ≤ 1`

    `<=> 0 ≤ 3cos² x ≤ 3`

    `<=> -1 ≤ 3cos^2 x – 1 ≤ 2`

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