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Q.Obtain the expression for rectangular components of a vector.

Manipur CohsemCouncil of Higher Secondary Education, Manipur (Higher Secondary 1st Year) 2023Subjective· 3mImportance★★★★★
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Resolving a vector along the x- and y-axes using right-triangle trigonometry gives Aₓ = A cosθ and Aᵧ = A sinθ.

Consider a vector A⃗\vec{A} lying in the x-y plane, making an angle θ\theta with the positive x-axis, with magnitude A=∣A⃗∣A = |\vec{A}|.

To find its rectangular (Cartesian) components, drop a perpendicular from the tip of A⃗\vec{A} onto the x-axis. This constructs a right-angled triangle with A⃗\vec{A} as the hypotenuse, the projection onto the x-axis as the base (AxA_x), and the projection onto the y-axis as the height (AyA_y).

From the definitions of sine and cosine in this right triangle:

Ax=Acos⁡θAy=Asin⁡θA_x = A\cos\theta \qquad A_y = A\sin\theta

So the vector can be written in terms of its components and the unit vectors i^\hat{i} (along x) and j^\hat{j} (along y) as:

A⃗=Axi^+Ayj^=Acos⁡θ i^+Asin⁡θ j^\vec{A} = A_x\hat{i} + A_y\hat{j} = A\cos\theta\,\hat{i} + A\sin\theta\,\hat{j}

Conversely, given the components Ax,AyA_x, A_y, the magnitude and direction of A⃗\vec{A} can be recovered: …

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