1.find the largest value of ( 1-2cosθ)^2 for 0度細等θ細等360度
2.find the value of the product: 1/3 X 1/9 X 1/27 X.... to 10terms 好係Sum of GS..但係中間係x唔係+喎
ans with explanation plz!
f.5 maths
2009-12-09 8:12 am
回答 (1)
2009-12-09 1:18 pm
✔ 最佳答案
rewrite Q1 ( 1-2cosA)^2 when cosA = -1
( 1-2cosA)^2
= [1- 2(-1)]^2
=3^2 =9
Q2
1/3 X 1/9 X 1/27 X....
= (1/3)(1/3^2)(1/3^3)...(1/3^10)
= [1/3^(1+2+3+.....+10)]
= 1/3^[(10)(11)/2]
= 1/3^55
收錄日期: 2021-04-13 16:58:33
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091209000051KK00024