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1d
comment The residue of $x^{15}-1$ divided by $x^2-1$
$$x((x^2)^7-1^7)+x-1$$ Now use math.stackexchange.com/questions/188657/…
1d
comment Finding an angle $\theta$ in a complex number
@XMLParsing, What is $\tan(A+B)=?$ But, I think math.stackexchange.com/questions/984416/… solves your problem of finding $t$
1d
comment How to find the equation of lines passing through the origin and perpendicular to the lines $xy-3y^2+y-2x+10=0$
@user103828, If you follow the trail, the rectification was already there, but not in the first line
1d
comment Find the equations of the two circles which pass through the point $(2,0)$ and have both the $y$-axis and the line $y-1=0$ as tangents
@hohner,What is the formula of the distance of a given point from a given line?
1d
comment Using induction for $x^n - 1$ is divisible by $x - 1$
math.stackexchange.com/questions/188657/…
1d
comment Proof of a formula for generalized Fibonacci numbers
An identity may be useful: $$U_rU_{n-1}-U_{r-1}U_n=U_rU_{n-1}-U_{r-1}(U_{n-1}+U_{n-2})=U_{n-1}[U_r-U_{r-1}]‌​-U_{r-1}U_{n-2}$$ $$\implies U_rU_{n-1}-U_{r-1}U_n=-(U_{r-1}U_{n-2}-U_{r-2}U_{n-1})$$
1d
comment Find the co-ordinates of the point of intersection
Set $y=-1$ to find $x$
1d
comment De Moivre's Theorem for proving
answers.yahoo.com/question/index?qid=20091201092452AACP5VB
1d
comment Partial Fractions (3 Factors)
mathworld.wolfram.com/PartialFractionDecomposition.html
1d
comment Proof of $\arcsin x \le 2\arctan x$?
@daw, Choice of increasing function?
1d
comment Proof that $ y(n) = ∑_{k=-∞}^{∞}\ {a}^{-k}u(n-k)u(-k) = \frac{1}{1-a }$ if $n>0$
en.wikipedia.org/wiki/Geometric_progression#Derivation
2d
comment Inverse Trigonometric Integrals
For the indefinite integral, can you try with Integration By Parts to derive a Reduction formula
2d
comment How to determine roots of a complex polynomial
@learningmaths, math.stackexchange.com/questions/690033/…
2d
comment Last 3 digits of $7^{12341}$
@rsadhvika, Using en.wikipedia.org/wiki/Carmichael_function, $$7^{12341}\equiv7^{41}\pmod{1000}$$
2d
comment Limit as x goes to infinity of this problem?
@Kaaagome, Please find the edited version
2d
comment Prove that $a$ cannot be a prime
$$\frac{a^2+b^2-c^2}{2ab}=\cos C=\cos60^\circ\implies a(a-b)=c^2-b^2$$
2d
comment How can I show that these integrals are zero
we can use mathworld.wolfram.com/WernerFormulas.html
Oct
19
comment Write $\sum_{k=0}^{\infty} \cos(k \pi / 6)$ in form $a+bi$
See math.stackexchange.com/questions/117114/…. But $$|e^{ia}|=1\not<1$$ So, we can not apply en.wikipedia.org/wiki/…
Oct
19
comment How to prove that $8^{18} - 1$ is divisible by $7$
Use math.stackexchange.com/questions/188657/…
Oct
19
comment Find the limit of a sequence $(\frac{z^n}{n!})_{n=1}^{\infty}$
$$e^x=\sum_{r=0}^\infty\frac{x^r}{r!}$$