用三角恆等式計
1. cos^3 θ +cos θ sin^2 θ
答案係cos θ
請問點計
請問條數點計
2007-03-01 4:00 am
回答 (3)
2007-03-01 4:05 am
✔ 最佳答案
cos^3 θ +cos θ sin^2 θ= cosθ (cos^2 θ + sin^2 θ) .......... but cos^2 θ + sin^2 θ = 1
= cos θ
2007-03-01 4:13 am
cos^3 θ +cos θ sin^2 θ
= cos θ (cos ^2 θ + sin ^ 2 θ)
= cos θ
(because cos ^2 θ + sin ^ 2 θ = 1)
cos ^ 3 θ = (cos θ)^3
cos θ sin^2 θ = cos θ (sin θ)^2
所以，兩項裏都有cos θ
抽公因數之後，才有第二行
就係甘多
希望可以幫到你
= cos θ (cos ^2 θ + sin ^ 2 θ)
= cos θ
(because cos ^2 θ + sin ^ 2 θ = 1)
cos ^ 3 θ = (cos θ)^3
cos θ sin^2 θ = cos θ (sin θ)^2
所以，兩項裏都有cos θ
抽公因數之後，才有第二行
就係甘多
希望可以幫到你
參考: 數學老師
2007-03-01 4:05 am
cos^3 θ +cos θ sin^2 θ
=cosθ(cos^2θ+sin^2θ)
=cosθx1
=cosθ
=cosθ(cos^2θ+sin^2θ)
=cosθx1
=cosθ
收錄日期: 2021-04-12 21:19:49
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070228000051KK03722