0<360
2COS^2 X +3SIN X=0
我做到最後
有sin x=1/2 or 2
x=30 or error
但answer係210 and330
help me呀
Maths,,,,,,hELP me ar,,,Maths急呀,,唔該
2007-11-11 8:22 pm
回答 (2)
2007-11-11 8:28 pm
✔ 最佳答案
2cos^2 x+3sinx=02(1-sin^2 x)+3sinx=0
2sin^2 x -3sinx-2=0
(2sinx+1)(sinx-2)=0
sin=-1/2 or sinx=2 (rejected)
sinx=-1/2
sinx=sin 180+30 or sin 360-30
x=210 or 330//
2007-11-11 8:30 pm
2COS^2 X +3SIN X=0
2[1-(sinx)^2] + 3 sin x = 0
2(sinx)^2 - 3sin x - 2 = 0
(sinx - 2) (2sinx + 1) = 0
sin x = -1/2
Quadrant III and IV will give sin x to be negative
x = 210 or x = 330
2[1-(sinx)^2] + 3 sin x = 0
2(sinx)^2 - 3sin x - 2 = 0
(sinx - 2) (2sinx + 1) = 0
sin x = -1/2
Quadrant III and IV will give sin x to be negative
x = 210 or x = 330
參考: My calculation
收錄日期: 2021-04-13 14:25:01
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071111000051KK01442