Find x,
sin4x + cos4x = sin 2x
A.Math -- trigonometry: [compound angles]
2006-12-15 4:36 am
回答 (1)
2006-12-15 4:45 am
✔ 最佳答案
sin^4x + cos^4x = sin 2x(sin^2x + cos^2x)^2 -2sin^2xcos^2x = sin2x
1-(1/2)sin^2(2x)=sin(2x)
sin^2(2x) + 2sin(2x) -2=0
sin(2x)=-1+√3 or -1-√3 (rej)
2x=180°n+(-1)^n(47.05°)
x=90°n+(-1)^n(23.5°)
收錄日期: 2021-04-12 21:22:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061214000051KK03797