Math  /  Calculus

QuestionQuestion
Given the function y=3x2sin4(x)y=3 x^{2} \sin ^{4}(x), find dydx\frac{d y}{d x} in any form. Note: make sure to write trig functions using parentheses like sin2(x)\sin ^{2}(x) instea interpreter might not be able to understand your expression.

Studdy Solution

STEP 1

1. The function y=3x2sin4(x) y = 3x^2 \sin^4(x) involves both polynomial and trigonometric components.
2. To find the derivative dydx\frac{d y}{d x}, we will need to use the product rule and the chain rule.

STEP 2

1. Apply the product rule to differentiate the function y=3x2sin4(x) y = 3x^2 \sin^4(x) .
2. Use the chain rule to differentiate sin4(x)\sin^4(x).

STEP 3

Identify the two functions involved in the product rule. Let u=3x2 u = 3x^2 and v=sin4(x) v = \sin^4(x) .
y=uv=3x2sin4(x) y = u \cdot v = 3x^2 \sin^4(x)

STEP 4

Recall the product rule for differentiation:
ddx(uv)=uv+uv \frac{d}{dx} (u \cdot v) = u' \cdot v + u \cdot v'

STEP 5

Differentiate u=3x2 u = 3x^2 with respect to x x :
u=ddx(3x2)=6x u' = \frac{d}{dx} (3x^2) = 6x

STEP 6

Differentiate v=sin4(x) v = \sin^4(x) with respect to x x using the chain rule. Let w=sin(x) w = \sin(x) , so v=w4 v = w^4 .
First, differentiate w4 w^4 with respect to w w :
ddw(w4)=4w3 \frac{d}{dw} (w^4) = 4w^3

STEP 7

Now, differentiate w=sin(x) w = \sin(x) with respect to x x :
ddx(sin(x))=cos(x) \frac{d}{dx} (\sin(x)) = \cos(x)

STEP 8

Apply the chain rule to combine these derivatives:
v=ddx(sin4(x))=4sin3(x)cos(x) v' = \frac{d}{dx} (\sin^4(x)) = 4 \sin^3(x) \cdot \cos(x)

STEP 9

Substitute u u , u u' , v v , and v v' into the product rule formula:
ddx(3x2sin4(x))=uv+uv \frac{d}{dx} (3x^2 \sin^4(x)) = u' \cdot v + u \cdot v' =6xsin4(x)+3x24sin3(x)cos(x) = 6x \cdot \sin^4(x) + 3x^2 \cdot 4 \sin^3(x) \cos(x)

STEP 10

Simplify the expression:
=6xsin4(x)+12x2sin3(x)cos(x) = 6x \cdot \sin^4(x) + 12x^2 \sin^3(x) \cos(x)

STEP 11

Write the final derivative:
dydx=6xsin4(x)+12x2sin3(x)cos(x) \frac{d y}{d x} = 6x \sin^4(x) + 12x^2 \sin^3(x) \cos(x)

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