The parametric equations are : $$ x=16\sin^3(t)$$ and $$y=13\cos(t)-5\cos(2t)-2\cos(3t)-\cos(4t) $$
with $t$ from $-\pi$ to $+\pi$
so I'm new to this kind of equations and i really don't know how to start the conversion... Can someone help me?
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On the right hand side, try using the formulas for the cosine of a sum. That is, $\cos(a+b)=\cos(a)\cos(b)-\sin(a)\sin(b)$, but replace the $a$ and $b$ with appropriate integer multiples of $t$. – Sinister Cutlass Nov 15 '15 at 19:51
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is this partial solution with the prosthaphaeresis formula correct: $y/1352=cos(1+2)-cos(3+4)$? – Cristian Nov 15 '15 at 19:58
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No. What you've written is that $y$ should be a constant value of $130\cdot [\cos(3)-\cos(7)]$, which is definitely not true. You can check that when you plug in $t$-values of $0$ and $\frac{\pi}{2}$ into the parametric equation for $y$, you get different output values for $y$. So $y$ can't be constant. – Sinister Cutlass Nov 15 '15 at 20:10
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ok, so if the y value cant be constat, how can i solve it (i should study much more...) – Cristian Nov 15 '15 at 20:16