Last updated on July 15th, 2025
We use the derivative of 4cos(x), which is -4sin(x), as a measure of how the cosine function changes in response to a slight change in x. Derivatives help us calculate profit or loss in real-life situations. We will now talk about the derivative of 4cos(x) in detail.
We now understand the derivative of 4cos x. It is commonly represented as d/dx (4cos x) or (4cos x)', and its value is -4sin x. The function 4cos x has a clearly defined derivative, indicating it is differentiable within its domain. The key concepts are mentioned below: Cosine Function: (cos(x) is the ratio of the adjacent side to the hypotenuse in a right triangle). Negative Sine Function: The derivative of cos(x) is -sin(x). Constant Multiplication Rule: Differentiating a constant multiplied by a function.
The derivative of 4cos x can be denoted as d/dx (4cos x) or (4cos x)'. The formula we use to differentiate 4cos x is: d/dx (4cos x) = -4sin x The formula applies to all x.
We can derive the derivative of 4cos x using proofs. To show this, we will use trigonometric identities along with the rules of differentiation. There are several methods we use to prove this, such as: By First Principle Using Chain Rule Using Product Rule We will now demonstrate that the differentiation of 4cos x results in -4sin x using the above-mentioned methods: By First Principle The derivative of 4cos x can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient. To find the derivative of 4cos x using the first principle, we will consider f(x) = 4cos x. Its derivative can be expressed as the following limit. f'(x) = limₕ→₀ [f(x + h) - f(x)] / h Given that f(x) = 4cos x, we write f(x + h) = 4cos(x + h). Substituting these into the equation, f'(x) = limₕ→₀ [4cos(x + h) - 4cos x] / h = 4limₕ→₀ [cos(x + h) - cos x] / h = 4limₕ→₀ [-2sin(x + h/2)sin(h/2)] / h = 4(-2)sin(x)limₕ→₀ [sin(h/2) / (h/2)] = -4sin(x) Hence, proved. Using Chain Rule To prove the differentiation of 4cos x using the chain rule, We use the formula: d/dx [4cos x] = 4 d/dx [cos x] The derivative of cos x is -sin x Therefore, d/dx (4cos x) = 4(-sin x) = -4sin x Using Product Rule We will now prove the derivative of 4cos x using the product rule. The step-by-step process is demonstrated below: Here, we use the formula, 4cos x = 4·(cos x) Given that, u = 4 and v = cos x Using the product rule formula: d/dx [u.v] = u'.v + u.v' u' = d/dx (4) = 0 v' = d/dx (cos x) = -sin x d/dx (4cos x) = 0·(cos x) + 4·(-sin x) = -4sin x
When a function is differentiated several times, the derivatives obtained are referred to as higher-order derivatives. Higher-order derivatives can be a little tricky. To understand them better, think of a car where the speed changes (first derivative) and the rate at which the speed changes (second derivative) also changes. Higher-order derivatives make it easier to understand functions like 4cos(x). For the first derivative of a function, we write f′(x), which indicates how the function changes or its slope at a certain point. The second derivative is derived from the first derivative, which is denoted using f′′(x). Similarly, the third derivative, f′′′(x), is the result of the second derivative, and this pattern continues. For the nth Derivative of 4cos(x), we generally use fⁿ(x) for the nth derivative of a function f(x), which tells us the change in the rate of change (continuing for higher-order derivatives).
When x is π/2, the derivative is -4sin(π/2), which is -4. When x is 0, the derivative of 4cos x = -4sin(0), which is 0.
Students frequently make mistakes when differentiating 4cos x. These mistakes can be resolved by understanding the proper solutions. Here are a few common mistakes and ways to solve them:
Calculate the derivative of (4cos x·x²)
Here, we have f(x) = 4cos x·x². Using the product rule, f'(x) = u′v + uv′ In the given equation, u = 4cos x and v = x². Let's differentiate each term: u′= d/dx (4cos x) = -4sin x v′= d/dx (x²) = 2x Substituting into the given equation, f'(x) = (-4sin x)·(x²) + (4cos x)·(2x) Let's simplify terms to get the final answer, f'(x) = -4x²sin x + 8xcos x Thus, the derivative of the specified function is -4x²sin x + 8xcos x.
We find the derivative of the given function by dividing the function into two parts. The first step is finding its derivative and then combining them using the product rule to get the final result.
A rotating fan blade's position is modeled by the function y = 4cos(x), where y represents the height of the blade at an angle x. If x = π/4 radians, determine the rate of change of the blade's height.
We have y = 4cos(x) (position of the blade)...(1) Now, we will differentiate equation (1) Take the derivative of 4cos(x): dy/dx = -4sin(x) Given x = π/4 (substitute this into the derivative) dy/dx = -4sin(π/4) dy/dx = -4(√2/2) = -2√2 Hence, the rate of change of the blade's height at x = π/4 is -2√2.
We find the rate of change of the blade's height at x = π/4, which means at this angle, the height of the blade is decreasing at a rate of -2√2.
Derive the second derivative of the function y = 4cos(x).
The first step is to find the first derivative, dy/dx = -4sin(x)...(1) Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx [-4sin(x)] The derivative of -4sin(x) is -4cos(x) Therefore, the second derivative of the function y = 4cos(x) is -4cos(x).
We use the step-by-step process, where we start with the first derivative. We then differentiate -4sin(x) to get -4cos(x) as the second derivative.
Prove: d/dx ((4cos(x))²) = -16cos(x)sin(x).
Let's start using the chain rule: Consider y = (4cos(x))² To differentiate, we use the chain rule: dy/dx = 2(4cos(x))·d/dx [4cos(x)] Since the derivative of 4cos(x) is -4sin(x), dy/dx = 2(4cos(x))·(-4sin(x)) dy/dx = -16cos(x)sin(x) Hence proved.
In this step-by-step process, we used the chain rule to differentiate the equation. Then, we replace 4cos(x) with its derivative. As a final step, we substitute y = (4cos(x))² to derive the equation.
Solve: d/dx (4cos(x)/x)
To differentiate the function, we use the quotient rule: d/dx (4cos(x)/x) = (d/dx (4cos(x))·x - 4cos(x)·d/dx(x))/x² We will substitute d/dx (4cos(x)) = -4sin(x) and d/dx(x) = 1 = ((-4sin(x))·x - 4cos(x)·1) / x² = (-4xsin(x) - 4cos(x)) / x² = -4(xsin(x) + cos(x)) / x² Therefore, d/dx (4cos(x)/x) = -4(xsin(x) + cos(x)) / x²
In this process, we differentiate the given function using the quotient rule. As a final step, we simplify the equation to obtain the final result.
Derivative: The derivative of a function indicates how the given function changes in response to a slight change in x. Cosine Function: The cosine function is a trigonometric function that represents the adjacent side over the hypotenuse in a right triangle. Sine Function: A trigonometric function that is the ratio of the opposite side to the hypotenuse in a right triangle. Chain Rule: A rule used to differentiate compositions of functions. Constant Multiplication Rule: A rule stating that the derivative of a constant times a function is the constant times the derivative of the function.
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.
: He loves to play the quiz with kids through algebra to make kids love it.