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7 Nov 2024
The integral \( \displaystyle \int \sin x \, dx \) is a basic result in calculus, and is used in various calculations involving trigonometry, wave motion, and oscillatory behavior.
The antiderivative of \( \sin x \) with respect to \( x \) is:
\[\begin{align*} \displaystyle \int \sin x \, dx = -\cos x + C, \end{align*}\]
where \( C \) is the constant of integration.
The derivative of \( -\cos x \) is \( \sin x \):
\[\begin{align*} \dfrac{d}{dx} -\cos x = \sin x \end{align*}\]
To reverse this process and find the integral, we integrate both sides. Thus integral \( \sin x \) yields a negative cosine function, reflecting the cyclical relationship between these trigonometric functions.
Integrating \( \sin x \) is useful in many contexts, such as in:
Problem: A machine part oscillates with velocity \( v(t) = 4 \sin(t) \) m/s. Find the position function \( s(t) \) if \( s(0) = 2 \).
Solution:
\[\begin{align*} s(t) = \displaystyle \int 4 \sin(t) \, dt = -4 \cos(t) + C. \end{align*}\]
Using \( s(0) = 2 \):
\[\begin{align*} -4 \cos(0) + C = 2 \Rightarrow -4 + C = 2 \Rightarrow C = 6. \end{align*}\]
So, \( s(t) = -4 \cos(t) + 6 \).