answer me this... this question was in my HSC paper which I was a bit unsure of...
a) Find all values of θ with 0≤θ≤2 pi such that sin θ-√(3) cosθ=1.
b)The difference between a real number r and the greatest integer less than or equal to r is called the fractional part of r, F(r). Thus F(3.45)=0.45.
Note that for all real numbers r, 0≤F(r)<1,
i) Let a =2136 log _(base 10)_ 2
Given that F(a)=7.0738... x 10^-5
observe that
F(2a)=14.1476... x 10^-5
F(3a)=21.2214... x 10^-5
(α) Use your calculator to show that
log_(base 10)_ 1.989 < F(4223a) < log_(base 10)_ 1.990.
(β) Hence calculate an integer M such that the ordinary decimal representation of 2^M begins with 1989. Thus 2^M=1989... .
ii) Let r be a real number and let m and n be non-zero integers with m ≪ n.
(α) Show that if F(mr)=0, then r is rational.
(β) Show that if F(mr)=F(nr), then r is rational.
iii) Suppose that b is an irrational number. Let N be a positive integer and consider the fractional parts F(b), F(2b), ..., F((N+1)b).
(α) Show that these N +1 numbers F(b), ..., F((N+1)b) are all distinct.
(β) Divide the interval 0≤x<1 into N subintervals each of length 1/N and show that there must be integers m and n with m ≪ n and 1 ≤ m, n ≤ N+1 such that F((m-n)b)<1/N.
iv) Given that log_(base 10)_2 is irrational, choose any integer N such that 1/N < log_(base 10)_ (1990/1989);
note that in (i), F(a) < log_(base 10)_ (1990/1989)
Use (iii) to decide whether there exists another integer M such that 2^M=1989....