cos 2x cos x 2 0

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begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell cos invisible function application 2 x minus cos invisible function application x minus 2 end cell equals 0 row cell open parentheses 2 cos squared invisible function application x minus 1 close parentheses minus cos invisible function application x minus 2 end cell equals 0 row cell 2 cos squared invisible function application x minus cos invisible function application x minus 3 end cell equals 0 row cell open parentheses cos invisible function application x plus 1 close parentheses open parentheses 2 cos invisible function application x minus 3 close parentheses end cell equals 0 row cell cos invisible function application x end cell equals cell negative 1 text atau end text cos invisible function application x equals 3 over 2 end cell end table end style

Karena -1 ≤ cos⁡ x ≤ 1, maka tak mungkin begin mathsize 14px style cos invisible function application x equals 3 over 2 end style.

Sehingga hanya cos⁡ x = -1 yg memenuhi.

Pada interval 0° ≤ x ≤ 360°, persamaan cos ⁡x = -1 cuma terpenuhi untuk x = 180° saja.

Sehingga himpunan solusi persamaan cos⁡ 2x − cos ⁡x − 2 = 0 pada interval 0° ≤ x ≤ 360° yakni 180° .

Makara, balasan yg sempurna ialah A.

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