particles in plane polar coordinates(adsbygoogle = window.adsbygoogle || []).push({});

r=rcosθ i + rsinθ k

F= F_{er}+ F_{eθ}

∂r/∂r =|∂r/∂r|_{er}= (cos^{2}θ + sin^{2}θ)½_{er}=er

why

∂r/∂θ =|∂r/∂θ|_{eθ}= (r^{2}cos^{2}θ + r^{2}sin^{2}θ)½_{eθ}= r_{eθ}

I understand that ∂r/∂θ = -rsinθ + rcosθ butwhy∂r/∂θ = (r^{2}cos^{2}θ + r^{2}sin^{2}θ)½_{eθ}

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# I Question about vector calculus

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