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If the sum of two of the roots of x3 + px2 + qx + r = 0 is zero, then pq =
sin-1 (sin 10 ) =
If f(x)=x, g(x)=ex−1, and ∫fog(x)dx=Afog(x)+Btan−1(fog(x))+C, then A+B is equal to:
It is given that, f(x)=x and g(x)=ex−1
Therefore, fog(x)=f(g(x))=ex−1
Now, it is also given that,
∫fog(x)dx=Afog(x)+Btan−1(fog(x))+C ----(1)
Therefore,
⇒∫fog(x) dx=∫ex−1 dx ----(2)
Let t=ex−1
⇒t2=ex−1
Differentiating both sides, we get,
⇒2t dt=ex dx
⇒2t dt=t2+1 dx(∵t2=ex−1)
⇒2tt2+1 dt=dx
Substituting this value in equation (2), we get,
⇒∫t.2tt2+1 dt=∫2t2t2+1 dt
⇒2∫t2+1−1t2+1 dt
⇒2∫t2+1t2+1 dt−2∫dtt2+1
⇒2∫dt−2∫dtt2+1
⇒2t−2tan−1t+C
Putting t=ex−1,
⇒2ex−1−2tan−1(ex−1)+C
We can write this equation as,
=2fog(x)−2tan−1(fog(x))+C
Comparing this equation with equation (1), we get A=2 and B=−2
Therefore, A+B=2+(−2)=0
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