About logarithmic functions:
according to a research of oceanography, for each metre that a diver goes down, light intensity will decrease by 2.5% How many metres should a diver go down such that
a) light intensity is one fourth of that at water surface? (Ans:55m)
b) light intensity is 1% of that at water surface? (Ans:182m)
About trico:
solve equation for 90<270,
a) 4cos^2A - 9cos(180+A)+2=0
(Ans: 104.48, 255.52)
b) 5cosA+2sin^2A+1=0
(Ans: 120, 240)
I want the steps...thanks...^^
F3...Maths questions X3
2007-06-11 1:11 am
回答 (1)
2007-06-11 1:36 am
✔ 最佳答案
a)let the diver go down q m(1-2.5%)^nq=1/4q
0.975^n=0.25
log(base=0.975)0.25=55(m)
b)(1-2.5%)^nq=0.01q
0.99^n=0.01
log(base=0.975)0.01=182m
a)4cos^2A - 9cos(180+A)+2=0
4cos^2A +9cos180+2=0
(4cosA+1)(cosA+2)=0
cosA=-0.25
A=104.48
therefore,the other ans is 360-104.48=255.52
b)5cosA+2sin^2A+1=0
2(1-cos^2A)+5cosA+1=0
2cos^2A-5cosA-3=0
(2cosA+1)(cosA-3)=0
cosA=-0.5
A=120 ,240
參考: me
收錄日期: 2021-04-13 00:52:00
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070610000051KK03422