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Last updated on September 15, 2025
We use the derivative of 2cos(x), which is -2sin(x), as a tool to understand how the cosine function changes with respect to a slight change in x. Derivatives help us analyze various real-world phenomena, such as oscillations and waves. We will now discuss the derivative of 2cos(x) in detail.
The derivative of 2cos(x) is represented as d/dx (2cos(x)) or (2cos(x))', and its value is -2sin(x). The function 2cos(x) has a well-defined derivative, indicating it is differentiable over its entire domain. Key points include:
Cosine Function: cos(x) is a basic trigonometric function.
Derivative of Cosine: The derivative of cos(x) is -sin(x).
Coefficient Impact: The coefficient '2' scales the derivative of cos(x) by a factor of 2.
The derivative of 2cos(x) can be denoted as d/dx (2cos(x)) or (2cos(x))'.
The formula we use to differentiate 2cos(x) is: d/dx (2cos(x)) = -2sin(x)
The formula is valid for all x in the domain of the cosine function.
We can derive the derivative of 2cos(x) using several methods. To demonstrate this, we will utilize trigonometric identities along with differentiation rules:
The derivative of 2cos(x) can be demonstrated using the First Principle, which defines the derivative as the limit of the difference quotient. Consider f(x) = 2cos(x). Its derivative is expressed as the limit: f'(x) = limₕ→₀ [f(x + h) - f(x)] / h
Given f(x) = 2cos(x), we write f(x + h) = 2cos(x + h).
Substituting these into the limit expression: f'(x) = limₕ→₀ [2cos(x + h) - 2cos(x)] / h = 2 limₕ→₀ [cos(x + h) - cos(x)] / h
Using the trigonometric identity: cos(x + h) - cos(x) = -2sin((2x + h)/2)sin(h/2) f'(x) = 2 limₕ→₀ [-2sin((2x + h)/2)sin(h/2)] / h = -2 limₕ→₀ [sin(h/2) / (h/2)]sin(x)
Using limit formulas, limₕ→₀ (sin(h/2) / (h/2)) = 1. f'(x) = -2sin(x) Hence, proved.
To prove the differentiation of 2cos(x) using the chain rule, Consider f(x) = cos(x) Then, 2cos(x) = 2 * f(x) The derivative of cos(x) is -sin(x).
Using the chain rule: d/dx(2cos(x)) = 2 * d/dx(cos(x)) = 2 * (-sin(x)) = -2sin(x)
We can also verify the derivative using the product rule: Consider 2cos(x) as a product: u = 2 and v = cos(x)
Using the product rule formula: d/dx [u * v] = u' * v + u * v' u' = d/dx(2) = 0 v' = d/dx(cos(x)) = -sin(x)
Then, d/dx(2cos(x)) = 0 * cos(x) + 2 * (-sin(x)) = -2sin(x)
When a function is differentiated multiple times, the resulting derivatives are higher-order derivatives. Understanding them can be complex.
Consider a pendulum, where the initial velocity (first derivative) and acceleration (second derivative) change. Higher-order derivatives help us analyze complex oscillatory functions like 2cos(x).
For the first derivative, we write f′(x), indicating the rate of change or slope at a specific point. The second derivative, denoted as f′′(x), is derived from the first derivative. Similarly, the third derivative, f′′′(x), results from the second derivative, and this pattern continues.
For the nth Derivative of 2cos(x), we use f^(n)(x), representing the rate of change of the (n-1)th derivative.
When x = π/2, the derivative is -2sin(π/2), which is -2, since sin(π/2) = 1.
When x = π, the derivative is -2sin(π), which is 0, since sin(π) = 0.
Students often make mistakes when differentiating 2cos(x). These can be avoided by understanding the correct process. Here are a few common mistakes and how to solve them:
Calculate the derivative of (2cos(x) * sin(x))
Here, we have f(x) = 2cos(x) * sin(x).
Using the product rule, f'(x) = u′v + uv′ In this case, u = 2cos(x) and v = sin(x).
Let's differentiate each term, u′ = d/dx(2cos(x)) = -2sin(x) v′ = d/dx(sin(x)) = cos(x)
Substituting into the product rule, f'(x) = (-2sin(x)) * sin(x) + (2cos(x)) * cos(x) = -2sin²(x) + 2cos²(x)
Thus, the derivative of the specified function is 2(cos²(x) - sin²(x)).
We find the derivative of the given function by differentiating each part separately and then combining them using the product rule to obtain the final result.
A lamp post of height h is situated on the ground. The shadow length is represented by the function y = 2cos(x), where y represents the shadow length at a given angle x. If x = π/3 radians, find the shadow length.
We have y = 2cos(x) (shadow length)...(1)
To find the shadow length, substitute x = π/3 into the equation: y = 2cos(π/3)
We know that cos(π/3) = 1/2. Therefore, y = 2 * (1/2) = 1.
Hence, the shadow length at x = π/3 is 1 unit.
We calculate the shadow length by substituting the given angle into the function y = 2cos(x) and simplifying using the known trigonometric value.
Derive the second derivative of the function y = 2cos(x).
The first step is to find the first derivative, dy/dx = -2sin(x)...(1)
Now, differentiate equation (1) to get the second derivative: d²y/dx² = d/dx[-2sin(x)] = -2cos(x)
Therefore, the second derivative of the function y = 2cos(x) is -2cos(x).
We use a step-by-step process where we start with the first derivative. By differentiating -2sin(x), we find the second derivative -2cos(x).
Prove: d/dx(4cos²(x)) = -8cos(x)sin(x).
Let's start using the chain rule: Consider y = 4cos²(x) = 4[cos(x)]²
To differentiate, we use the chain rule: dy/dx = 4 * 2cos(x) * d/dx[cos(x)]
Since the derivative of cos(x) is -sin(x), dy/dx = 8cos(x) * (-sin(x)) = -8cos(x)sin(x)
Hence proved.
We use the chain rule to differentiate the equation. Then, we replace cos(x) with its derivative and simplify the expression to derive the equation.
Solve: d/dx (2cos(x)/x)
To differentiate the function, we use the quotient rule: d/dx (2cos(x)/x) = (d/dx(2cos(x)) * x - 2cos(x) * d/dx(x))/x²
We substitute d/dx(2cos(x)) = -2sin(x) and d/dx(x) = 1 = (-2sin(x) * x - 2cos(x))/x² = (-2xsin(x) - 2cos(x))/x²
Therefore, d/dx (2cos(x)/x) = (-2xsin(x) - 2cos(x))/x²
We differentiate the given function using the quotient rule and simplify the expression to obtain the final result.
Jaskaran Singh Saluja is a math wizard with nearly three years of experience as a math teacher. His expertise is in algebra, so he can make algebra classes interesting by turning tricky equations into simple puzzles.
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