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F3...Maths questions X3
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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?... 顯示更多 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
最佳解答:
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
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