Integral Calculus: JEE Main Mathematics Question with Solution
The value of π8∫02π(sinx)2023+(cosx)2023(cosx)2023dx is
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Hint 1 of 3
Let I=∫02π(sinx)2023+(cosx)2023(cosx)2023dx. What equivalent integral is obtained by applying the property ∫abf(x)dx=∫abf(a+b−x)dx?
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Step-by-step solutionView
Correct answer
The integral evaluates to 4π, so multiplying by π8 gives an answer of 2.
Option analysis
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Reviewed route
Solution
StepWorking
01given
Let the given expression be J=π8I, where I=∫02π(sinx)2023+(cosx)2023(cosx)2023dx.
02goal
Evaluate J=π8I.
03approach
Apply King's property ∫abf(x)dx=∫abf(a+b−x)dx with a=0 and b=2π, then add the two representations of I.
04execute
Using x→2π−x, we get cos(2π−x)=sinx and sin(2π−x)=cosx. Thus:
I=∫02π(cosx)2023+(sinx)2023(sinx)2023dx
Adding the two forms of I:
2I=∫02π(sinx)2023+(cosx)2023(cosx)2023+(sinx)2023dx=∫02π1dx=2π
Therefore, I=4π.
05execute
Now multiply by the prefactor π8:
J=π8I=π8×4π=2
✓verify
By symmetry of f(x)+f(π/2−x)=1 over [0,π/2], the average value of the integrand is 21. The integral is 21×2π=4π. Multiplying by π8 gives 2.
Hints that build this answer step by step
Let I=∫02π(sinx)2023+(cosx)2023(cosx)2023dx. What equivalent integral is obtained by applying the property ∫abf(x)dx=∫abf(a+b−x)dx?
I=∫02π(cosx)2023+(sinx)2023(sinx)2023dx
Adding the original expression for I to the transformed expression yields 2I. What does the integrand simplify to?