I = ∫ e 6 π e π x sin ( lo g ( x ) ) sin ( lo g ( sin ( lo g ( x ) ) ) ) cos ( lo g ( x ) ) d x
If I can be expressed in the form A + cos ( B ) , where A and B are real numbers, A is a negative integer, and B is the smallest possible positive number that satisfies the value of I , find I + A + B to 2 decimal places.
NOTE:
lo g ( x ) denotes the natural logarithm of x .
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Limits on the integral are wrong, aside from that, nice work. :) Same here.
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Oh sorry. I just copied the same limits on the previous integral. Fixed it.
A nice desinged easy sum. Good one! +1 from me!
Hey @Akeel Howell you can keep the lower limit as 6 e π
the answer would be , acc. to me , -2+cos(ln2))-ln2 instead of + , check it again , the exact value of B i get is ln(1/2) , pl check it .
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Relevant wiki: u -Substitution
I = ∫ 6 e π e π x sin ( lo g ( x ) ) sin ( lo g ( sin ( lo g ( x ) ) ) ) cos ( lo g ( x ) ) d x
We can use a substitution to simplify the integrand. We see this instantly if we set u = lo g ( sin ( lo g ( x ) ) ) . This gives that d u = x sin ( lo g ( x ) ) cos ( lo g ( x ) ) d x .
This leaves us with I = ∫ − lo g 2 0 sin ( u ) d u = − cos ( u ) . Substituting again to have u in terms of x , we see that I = − cos ( lo g ( sin ( lo g ( x ) ) ) ) ∣ 6 e π e π So I = − 1 + cos ( lo g ( 2 ) ) Thus, A = − 1 and B = lo g ( 2 ) . ∴ I + A + B = − 1 + cos ( lo g ( 2 ) ) − 1 + lo g ( 2 ) ≈ − 0 . 5 4 ( 2 decimal places )