MHB -11.7.94 Find the rectangular equation

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The discussion focuses on finding the rectangular equation for the polar curve defined by r = sin(θ + π/4). The transformation involves using trigonometric identities to express r in terms of x and y, ultimately leading to the equation x² + y² = (√2/2)(x + y). This simplifies to the standard form of a circle, resulting in the equation (x - √2/4)² + (y - √2/4)² = (1/2)². The conclusion emphasizes that the curve represents a circle in the Cartesian coordinate system.
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$\tiny{11.7.94 Kamahamai HS}$
Find the rectangular equation of the curve $r=\sin\left(\theta+\dfrac{\pi}{4}\right)$
$r=\sin \theta{\cos \dfrac{\pi}{4}
+{\cos \theta{\sin \dfrac{\pi}{4}}}}
=\sin \theta\left(\dfrac{\sqrt{2}}{2}\right)+\cos \theta\left(\dfrac{\sqrt{2}}{2}\right)
=\left(\dfrac{\sqrt{2}}{2}\right) (\sin \theta+\cos\theta)$

well so far anyway
Desmos plotted a circle
 
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$r = \dfrac{\sqrt{2}}{2}(\cos{t}+\sin{t})$

$r^2 = \dfrac{\sqrt{2}}{2}(r\cos{t}+r\sin{t})$

$x^2+y^2 = \dfrac{\sqrt{2}}{2}(x+y)$

which leads to …

$\left(x-\dfrac{\sqrt{2}}{4}\right)^2 + \left(y - \dfrac{\sqrt{2}}{4}\right)^2 = \left(\dfrac{1}{2}\right)^2$
 
so that's how you get a circle 🙄
https://dl.orangedox.com/QS7cBvdKw55RQUbliE
 
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