Melody

Thanks Alan,

I'm still scratching my head on this one. (contemplation and confusion - not nits   LOL )

$$\\2m(3m+1)\\\\
=2m*3m\;\;+\;\;2m*1\\\\
=6m^2\;\;+\;\;2m$$

10x+3x=13x

so

13x=169

now divide both sides by 13  

I am jut going to REDO it here   :))

$$\\y=18.5+6sin((9(\pi/12)) - (10(\pi/12)))\\\\
y=18.5+6sin(9\pi/12 - 10\pi/12)))\\\\
y=18.5+6sin(-\pi/12)))\\\\
$ 4th quad so neg$\\\\
y=18.5-6sin(\pi/12)))\\\\
y=18.5-6sin(15^0)\\\\
y=18.5-6sin(45-30)\\\\
y=18.5-6[sin45cos30-cos45sin30]\\\\
y=18.5-6[\frac{1}{\sqrt2}*\frac{\sqrt3}{2}-\frac{1}{\sqrt2}*\frac{1}{2}]\\\\$$

$$\\y=18.5-6[\frac{\sqrt3}{2\sqrt2}-\frac{1}{2\sqrt2}]\\\\
y=18.5-6[\frac{\sqrt6}{4}-\frac{\sqrt2}{4}]\\\\
y=18.5-3[\frac{\sqrt6}{2}-\frac{\sqrt2}{2}]\\\\
y=\frac{37-3\sqrt6+3\sqrt2}{2}\\\\$$

Ok NOW our answers are the same :))

Yes you are right. Thanks for noticing that :)

 Sorry anon  :/

Well that is great :)

64x^6-80x^4+8x^3+24x^2-4x-1=0

64*(cos(2pi/11))^6-80*(cos(2pi/11))^4+8*(cos(2pi/11))^3+24*(cos(2pi/11))^2-4*(cos(2pi/11))-1

$${\mathtt{64}}{\mathtt{\,\times\,}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{{\mathtt{360}}}{{\mathtt{11}}}}\right)}}^{\,{\mathtt{6}}}{\mathtt{\,-\,}}{\mathtt{80}}{\mathtt{\,\times\,}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{{\mathtt{360}}}{{\mathtt{11}}}}\right)}}^{\,{\mathtt{4}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\times\,}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{{\mathtt{360}}}{{\mathtt{11}}}}\right)}}^{\,{\mathtt{3}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{24}}{\mathtt{\,\times\,}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{{\mathtt{360}}}{{\mathtt{11}}}}\right)}}^{\,{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{4}}{\mathtt{\,\times\,}}\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\frac{{\mathtt{360}}}{{\mathtt{11}}}}\right)}{\mathtt{\,-\,}}{\mathtt{1}} = -{\mathtt{0.000\: \!000\: \!000\: \!004\: \!464\: \!9}}$$

Yes it looks like you might be right - it is certainly is very close to zero :)

I am not so sure that Wolfram|Alpha agrees with you though.  

CONTINUED  HERE

Thiere is a mistake in this one so you had best ignore it ://

$$\\y=18.5+6sin((9(\pi/12)) - (10(\pi/12)))\\\\
y=18.5+6sin(3\pi/4) - (5\pi/6)\\\\
y=18.5+6sin(3\pi/4) - (5\pi/6)\\\\
$second quad so the sine is positive$\\\\
y=18.5+6sin(\pi-\3pi/4) - (5\pi/6)\\\\
y=18.5+6sin(\pi/4) - (5\pi/6)\\\\
y=18.5+6*\frac{1}{\sqrt2} - (5\pi/6)\\\\
y=18.5+6*\frac{1*\sqrt2}{\sqrt2*\sqrt2} - (5\pi/6)\\\\
y=18.5+6*\frac{\sqrt2}{2} - (5\pi/6)\\\\
y=18.5+3\sqrt2 - \frac{5\pi}{6}\\\\$$

2nd.    asin  angle

Or

asIn(angle)

asin stands for arc sine which is the same as inverse sine :)