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May 8[edit]

sin(sin t)?[edit]

What is the solution to t = sin(sin t)? In other words, how can I find all points common to the helices C_1 and C_2 where C_1(t) = (cos t, sin t, t), t is real; and C_2(s) = (cos s, s, sin s), s is real? 60.240.101.246 (talk) 03:23, 8 May 2010 (UTC)[reply]

t=0 is the obvious one... 69.228.170.24 (talk) 04:53, 8 May 2010 (UTC)[reply]

...and t=0 is the only solution (assuming t is in radians), because

{\frac {d}{dt}}(t-\sin(\sin(t)))=1-\cos(t)\cos(\sin(t))

which is 0 at t=0, and

{\frac {d^{2}}{dt^{2}}}(t-\sin(\sin(t)))=\sin(t)\cos(\sin(t))+\cos ^{2}(t)\sin(\sin(t))

which is also 0 when t=0, but positive away from t=0, so slope of t-sin(sin(t)) increases as you move away from 0 in either direction. So helices only intersect at (1,0,0). Gandalf61 (talk) 09:26, 8 May 2010 (UTC)[reply]

(EC) And note that for t≠0 |sin(sin(t))|≤|sin(t)|<|t|, so there's no other solution.--84.221.69.102 (talk) 10:33, 8 May 2010 (UTC)[reply]

If we write

\arcsin t=\sin t\,

and take "arcsin" to mean the "multiple-valued" arcsine, and look at the two graphs superimposed on each other, it becomes obvious that they intersect only once. Therefore only the trivial solution t = 0 exists. Michael Hardy (talk) 03:37, 10 May 2010 (UTC)[reply]

The function

\scriptstyle f(t)=t-\sin(\sin t)

is an odd function:

\scriptstyle (f(-t)=-f(t))

, and the function value of the complex conjugate argument is the complex conjugate function value of the argument:

\scriptstyle (f({\overline {t}})={\overline {f(t)}})

. This implies that if

\scriptstyle r

is a root,

\scriptstyle (f(r)=0)

, then so is

\scriptstyle -r

and

\scriptstyle {\overline {r}}

and

\scriptstyle -{\overline {r}}

. Some nonzero roots are ±1.7856225020975647±2.8984466947375185i, ±2.2559594166866765±1.7316525254965243i, ±4.9222858483025655±3.1622510760997686i, and ±36.13956703186652±6.6383288953460431i. Bo Jacoby (talk) 13:29, 12 May 2010 (UTC).[reply]

The armed force of Ghana ...[edit]

                                                                  QUESTION    1

The armed forces of Ghana want an algorithm that can efficiently solve a particular decision problem T in the worst –case.Three algorithms are currently available .They are A,B and C with running times , T_A (n)={█(4T_A (n-1) + Ѳ(2^n) , n>0@6 , n=0 )┤ T_B (n)={█(Ѳ(1) if 1≤n<3@2T_B (⌊n/3⌋) + Ѳ(T_A (n) ) if n≥3)┤ T_C (n)={█(Ѳ(1) if 1≤n≤3@2T(⌈n/3⌉ ) + Ѳ(n) if n≥3)┤ (i) Explain why B should not be in the list (ii) Which program ( A,B or C ) would you recommend to the armed forces .Justify your answer.

                                                                   QUESTION 2

The population at time N U {0} of two nations Messi and Xavi , are noted by the recurrence relation ,

X(n)={█(rX(n-1) + g(n) if n>0@a if n=0)┤ and M(n) ={█(3T(⌈n/3⌉ ) + n√(n+1) if n>1@2 if 0≤n≤1 )┤respectively where a , r ∈ N and g is defined on the positive integers .Show that X(n) = r^n a + ⋋∑_(i=1)^n▒r^(n-1) g(i) for some constant ⋋ ∈ R . Hence or otherwise determine the value of lim┬(n⟶∞)⁡〖(M(n))/(X(n))〗 if r=4 a=6 and g(n)=2^(n ).

Find Big-oh expression for X(n) and M(n) . —Preceding unsigned comment added by Waslimp (talk • contribs) 12:00, 8 May 2010 (UTC)[reply]

Please explain what aspect of these problems you are needing help with. How far have you got with your analysis? BTW I see a big black square between the { and the ( in X(n)={█(rX(n-1). What is it meant to be? -- SGBailey (talk) 14:31, 8 May 2010 (UTC)[reply]

This post is just a repetition of a "Discrete_maths" question above dated May 7 (maybe both could be removed) --pm a 07:04, 9 May 2010 (UTC)[reply]