Which expression is equal to \[ \int sin^2(2x)dx \]?
(A) \( \frac{1}{2} \left( x - \frac{1}{4}sin(4x) \right) + c \)
(B) \( \frac{1}{2} \left( x + \frac{1}{4}sin(4x) \right) + c \)
(C) \( sin^3(2x) \) + c
(D) \( -\frac{cos^2(2x)}{6} \) + c - HSC - SSCE Mathematics Extension 1 - Question 5 - 2016 - Paper 1
Question 5
Which expression is equal to \[ \int sin^2(2x)dx \]?
(A) \( \frac{1}{2} \left( x - \frac{1}{4}sin(4x) \right) + c \)
(B) \( \frac{1}{2} \left( x + \frac{1}{4}sin... show full transcript
Worked Solution & Example Answer:Which expression is equal to \[ \int sin^2(2x)dx \]?
(A) \( \frac{1}{2} \left( x - \frac{1}{4}sin(4x) \right) + c \)
(B) \( \frac{1}{2} \left( x + \frac{1}{4}sin(4x) \right) + c \)
(C) \( sin^3(2x) \) + c
(D) \( -\frac{cos^2(2x)}{6} \) + c - HSC - SSCE Mathematics Extension 1 - Question 5 - 2016 - Paper 1
Step 1
Determine the integral \( \int sin^2(2x)dx \)
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Answer
To solve ( \int sin^2(2x)dx ), we can use the identity ( sin^2(u) = \frac{1 - cos(2u)}{2} ).
Applying this identity, we can write:
[ \int sin^2(2x)dx = \int \frac{1 - cos(4x)}{2}dx ]
This can be split into two parts:
[ \frac{1}{2} \int dx - \frac{1}{2} \int cos(4x)dx ]
Step 2
Evaluate the integrals
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Answer
The first integral is straightforward:
[ \frac{1}{2} \int dx = \frac{x}{2} + C_1 ]
For the second integral, we have:
[ -\frac{1}{2} \int cos(4x)dx = -\frac{1}{2} \frac{1}{4}sin(4x) + C_2 = -\frac{1}{8}sin(4x) + C_2 ]
Combining these results, we get:
[ \int sin^2(2x)dx = \frac{x}{2} - \frac{1}{8}sin(4x) + C ]
Step 3
Final expression
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Answer
Thus, the final expression for the integral ( \int sin^2(2x)dx ) is:
[ \frac{1}{2} \left( x - \frac{1}{4}sin(4x) \right) + c ]
This corresponds to option (A), which is the correct answer.