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2d
comment Trigonometric ratios
Use $$\cos A=\frac{b^2+c^2-a^2}{2bc}$$ to find $AB=c$ Then use the other hint
2d
answered Conjecture about the units digit of 9^n where n is a positive integer
2d
comment $\tan \{\frac{1}{2} \sin^{–1} (2x/ 1 + x^2) + \frac{1}{2} \cos^{–1} (1 – y^2/1 + y^2) \}$ is equal to.
@user185262, I've updated answer for you. Please let me know if it's not sufficient.
2d
revised $\tan \{\frac{1}{2} \sin^{–1} (2x/ 1 + x^2) + \frac{1}{2} \cos^{–1} (1 – y^2/1 + y^2) \}$ is equal to.
added 979 characters in body
Oct
18
comment $\tan \{\frac{1}{2} \sin^{–1} (2x/ 1 + x^2) + \frac{1}{2} \cos^{–1} (1 – y^2/1 + y^2) \}$ is equal to.
@user185262, Have you reached the destination ? Else see en.wikipedia.org/wiki/…
Oct
18
answered $\tan \{\frac{1}{2} \sin^{–1} (2x/ 1 + x^2) + \frac{1}{2} \cos^{–1} (1 – y^2/1 + y^2) \}$ is equal to.
Oct
18
comment Prove that for all positive integers $x$, $\left\lfloor \frac{x^2 +2x + 2}{4}\right\rfloor =\left\lfloor \frac{x^2 + 2x + 1}{4}\right\rfloor$.
Wish I know the mistake here
Oct
17
answered Take the derivative of $f(x)$
Oct
17
comment What does the notation $\equiv 1\ (\text{mod}\ p)$ mean?
mathworld.wolfram.com/Congruence.html
Oct
17
comment Simplify: $\sin \frac{2\pi}{n} +\sin \frac{4\pi}{n} +\ldots +\sin \frac{2\pi(n-1)}{n}$.
Related : math.stackexchange.com/questions/17966/…
Oct
17
comment Help with a limit $S_{n}=\frac{1}{n}\sum _{k=1}^{n} \sqrt{\frac{k}{n}}$
@IvanSGuerra, Related: math.stackexchange.com/questions/465075/…
Oct
16
answered Discrete algebra and exponents (See body text)
Oct
16
comment Intersection points of two trignometric equations
@lucax, We need $0\le2n\pi+\dfrac\pi2\le2\pi\iff0\le4n+1\le4\implies n=0$ and similarly, $$0\le r\pi+(-1)^r\left(-\frac\pi6\right)\le2\pi$$ Check for even$(2m)$ & odd$(2m+1)$ values of $r$
Oct
16
answered Prove that for all positive integers $x$, $\left\lfloor \frac{x^2 +2x + 2}{4}\right\rfloor =\left\lfloor \frac{x^2 + 2x + 1}{4}\right\rfloor$.
Oct
16
answered Sum of $\sin$ and $\cos$
Oct
16
answered Verify the trig formula with complex representation
Oct
16
answered Verify Euler's formula
Oct
16
answered Intersection points of two trignometric equations
Oct
16
answered Intersection points of two trignometric equations
Oct
16
answered How to calculate $\lim_{x \rightarrow \infty} (4x\arctan(x)-2\pi x)$