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Last updated on September 10, 2025
We use the derivative of 5cos(x), which is -5sin(x), as a measuring tool for 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 5cos(x) in detail.
We now understand the derivative of 5cosx. It is commonly represented as d/dx (5cosx) or (5cosx)', and its value is -5sinx.
The function 5cosx has a clearly defined derivative, indicating it is differentiable within its domain. The key concepts are mentioned below:
Cosine Function: (cos(x)).
Constant Rule: Rule for differentiating constants multiplied by a function.
Sine Function: sin(x) is the derivative of cos(x).
The derivative of 5cosx can be denoted as d/dx (5cosx) or (5cosx)'.
The formula we use to differentiate 5cosx is: d/dx (5cosx) = -5sinx (or) (5cosx)' = -5sinx
The formula applies to all x.
We can derive the derivative of 5cosx using proofs. To show this, we will use the trigonometric identities along with the rules of differentiation. There are several methods we use to prove this, such as:
We will now demonstrate that the differentiation of 5cosx results in -5sinx using the above-mentioned methods:
The derivative of 5cosx can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient.
To find the derivative of 5cosx using the first principle, we will consider f(x) = 5cosx. Its derivative can be expressed as the following limit. f'(x) = limₕ→₀ [f(x + h) - f(x)] / h … (1)
Given that f(x) = 5cosx, we write f(x + h) = 5cos(x + h).
Substituting these into equation (1), f'(x) = limₕ→₀ [5cos(x + h) - 5cosx] / h = limₕ→₀ 5[cos(x + h) - cosx] / h = 5limₕ→₀ [-2sin((x + x + h)/2)sin(h/2)] / h
Using the formula for the limit, sin(h/2)/(h/2) = 1 as h approaches 0, we have: f'(x) = 5[-2sin(x) * 1] = -5sinx. Hence, proved.
To prove the differentiation of 5cosx using the chain rule, We use the formula:
5cosx = 5 * cosx Consider u(x) = 5 and v(x) = cosx.
Using the product rule: d/dx [u(x) * v(x)] = u'(x) * v(x) + u(x) * v'(x)
Let’s substitute u(x) = 5 and v(x) = cosx, d/dx (5cosx) = 0 * cosx + 5 * (-sinx) = -5sinx.
We will now prove the derivative of 5cosx using the product rule. The step-by-step process is demonstrated below: Here, we use the formula, 5cosx = (5).(cosx) Given that, u = 5 and v = cosx
Using the product rule formula: d/dx [u.v] = u'.v + u.v' u' = d/dx (5) = 0 v' = d/dx (cosx) = -sinx
Again, use the product rule formula: d/dx (5cosx) = u'v + uv' = 0 * cosx + 5 * (-sinx) = -5sinx.
Thus: d/dx (5cosx) = -5sinx.
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 5cos(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 5cos(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 the x is π/2, the derivative is -5sin(π/2), which is -5. When the x is 0, the derivative of 5cosx = -5sin(0), which is 0.
Students frequently make mistakes when differentiating 5cosx. 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 (5cosx·sinx)
Here, we have f(x) = 5cosx·sinx. Using the product rule, f'(x) = u′v + uv′ In the given equation, u = 5cosx and v = sinx.
Let’s differentiate each term, u′= d/dx (5cosx) = -5sinx v′= d/dx (sinx) = cosx
Substituting into the given equation, f'(x) = (-5sinx)(sinx) + (5cosx)(cosx)
Let’s simplify terms to get the final answer, f'(x) = -5sin²x + 5cos²x
Thus, the derivative of the specified function is -5sin²x + 5cos²x.
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 company is analyzing the oscillation of a pendulum. The position is represented by the function y = 5cos(x) where y represents the displacement at time x. If x = π/3 seconds, measure the rate of change of displacement.
We have y = 5cos(x) (position of the pendulum)...(1)
Now, we will differentiate the equation (1)
Take the derivative of 5cos(x): dy/dx = -5sin(x) Given x = π/3 (substitute this into the derivative)
dy/dx = -5sin(π/3) dy/dx = -5 * (√3/2) dy/dx = -5√3/2
Hence, we get the rate of change of displacement at x = π/3 as -5√3/2.
We find the rate of change of displacement at x = π/3 as -5√3/2, which means that at this point, the displacement is decreasing by -5√3/2 units per second.
Derive the second derivative of the function y = 5cos(x).
The first step is to find the first derivative, dy/dx = -5sin(x)...(1)
Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx [-5sin(x)] = -5cos(x)
Therefore, the second derivative of the function y = 5cos(x) is -5cos(x).
We use the step-by-step process, where we start with the first derivative. Using the derivative of sin(x), we find that the second derivative of 5cos(x) is -5cos(x).
Prove: d/dx ((5cosx)²) = -10cosxsinx.
Let’s start using the chain rule: Consider y = (5cosx)² = [5cos(x)]²
To differentiate, we use the chain rule: dy/dx = 2[5cos(x)] * d/dx [5cos(x)]
Since the derivative of 5cos(x) is -5sin(x), dy/dx = 2[5cos(x)] * -5sin(x) = -10cos(x)sin(x)
Hence proved.
In this step-by-step process, we used the chain rule to differentiate the equation.
Then, we replaced the derivative of 5cos(x) with -5sin(x). As a final step, we simplified to derive the equation.
Solve: d/dx (5cosx/x)
To differentiate the function, we use the quotient rule: d/dx (5cosx/x) = (d/dx (5cosx) * x - 5cosx * d/dx(x))/x²
We will substitute d/dx (5cosx) = -5sinx and d/dx(x) = 1 = (-5sinx * x - 5cosx * 1) / x² = (-5xsinx - 5cosx) / x² = -5(xsinx + cosx) / x²
Therefore, d/dx (5cosx/x) = -5(xsinx + cosx) / 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.
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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