F.4 Maths

2010-02-28 8:27 pm

Solve the following equation for 0°≤x≤360°.
(Give your answers correct to 1 decimal place if necessary.)

cos2x= -0.5

回答 (2)

2010-02-28 8:52 pm

✔ 最佳答案

cos2x= -0.5
2x=120°,300°,480°,660°
x=60°,150°,240°,330°

2010-02-28 12:54:19 補充：
It my mistake
cos2x= -0.5
2x=120°,240°,480°,°
x=60°,120°,240°,300°

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2010-02-28 8:52 pm

cos2x = -0.5

2x = 180° ± 60° or x = 360° + (180° ± 60°)

x = 60°, 120°, 240°, 300°

參考: 老爺子

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