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#52 Re: Exercises » cos(x - y) » 2010-09-06 01:17:29

cosx +cosy=a
sinx-siny=b
squarring bot the equation then subtrac
cos2x+cos2y+2cox(x-y)=a2-b2
2cos(x-y)[1+cos(x+y)]=a^2-b^2  (o)

now squarring above equation then add
cos(x+y)=(a^2+b^2)/2-1
now put the valu of cos(x+y) in (o)
cos(x-y)=a2 -b2/a2+b2

#53 Re: Help Me ! » provement » 2010-09-06 00:52:12

what is range of
F(x)=1/(3-5cosx)

#54 Re: Help Me ! » provement » 2010-09-03 21:53:58

what is area of triangle with sides 1-(x^1/2),5-(x^1/2),7-(x^1/2)
what is eaist method to solve it

#55 Re: Help Me ! » Points of Inflection.. » 2010-09-03 21:29:16

hi carisma
point of inflection is that point where a function changes its nature i.e(it changes its sign from + to - & vice versa)
or mathmatically you can say doubble derivative zero or does not exist at that point

2nd derivative does not exist means in the graph of frist derivative there will be sudden change at that point
in your Q. f(x)= e^(-2x^2)
f"(x)=0 at x=1/2,-1/2
according to condition x=-1/2 is point of inflection

#56 Re: Help Me ! » provement » 2010-09-02 21:17:46

if "3x+4y+5z=12"
then what is minimum valu of x^2+y^2+z^2

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