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Dec
10
comment Calculate the result of the following sequence.
@FuriousMathematician, See en.wikipedia.org/wiki/Arithmetico-geometric_sequence
Dec
10
comment What is the exact value of $\cos\left(\arccos\dfrac{1}{7}+\arcsin\dfrac{1}{5}\right)$
Follow math.stackexchange.com/questions/1059572/…
Dec
10
answered Just a proof of algebra
Dec
10
comment Prove that : $f(\sin x)+f(\cos x) \ge 196, \forall x\in\left(0;\frac{\pi}{2}\right)$
Was solving in the same line, but didn't refresh :) (+1)
Dec
10
comment Evaluating derivative of $\int^{3x}_{2x} \sin(t^3 + 1) \,\mathrm dt$
Use en.wikipedia.org/wiki/Differentiation_under_the_integral_sign and en.wikipedia.org/wiki/Leibniz_integral_rule
Dec
10
comment What is the value of the constant C?
@TdOt, Have you heard of parametric form?
Dec
9
comment Finding exact value of trigonometric functions
@Astroman, Yes, so we need all four $:\cos A,\cos B,\sin A,\sin B$
Dec
9
comment Using the half/double angle formulas to solve an equation
Are you sure that you need to use half/double angle formulas?
Dec
9
comment Finding exact value of trigonometric functions
@Astroman, What's $\cos(A+B)$
Dec
9
comment Using the half/double angle formulas to solve an equation
@Cherry_Developer, Squaring either sides & using $\cos2A=1-2\sin^2A$ is another option which needs the elimination of extraneous roots
Dec
9
comment Finding exact value of trigonometric functions
@Astroman, Please share your method
Dec
9
revised System of congruences with not coprime numbers
added 179 characters in body
Dec
9
answered System of congruences with not coprime numbers
Dec
9
answered Finding exact value of trigonometric functions
Dec
9
answered Sequence limit…
Dec
9
comment Help with $\int \frac{1}{(\sin x + \cos x)}$
@fvel, If $a<0, b\ge0,$ $\arctan 2(y,x)=\arctan\dfrac yx+\pi$ $$\implies\sin[x+\arctan2(y,x)]=\sin[\pi+x+\arctan\dfrac yx]=-\sin[x+\arctan\dfrac yx]$$ etc.
Dec
9
revised Help with $\int \frac{1}{(\sin x + \cos x)}$
added 214 characters in body
Dec
9
answered How to solve $\sin\theta +\sin3\theta =0$
Dec
9
comment Sequence limit…
@vilinia, See mathworld.wolfram.com/RiemannIntegral.html
Dec
9
comment Help with $\int \frac{1}{(\sin x + \cos x)}$
@fvel, I would like use en.wikipedia.org/wiki/Atan2#Definition_and_computation in place of sgn$(a)$