Engineering
Mathematics
Integration of Trigonometric Functions
Integration by Substitution
Question

Let α∈(0,π2) be fixed. If the integral ∫tanx+tanαtanx−tanα dx = A(x) 2α + B(x) sin 2α + C, where C is a constant of integration then the functions A(x) and B(x) are respectively :

x + α and loge |sin(z + α)|

x + α and loge |sin(x – α)|

x – α and loge |sin(x – α)|

x – α and loge |cos(x – α)|

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Solution

∫sinxcosα+cosxsinαsinx cosα−cos x sin αdxo

=∫sin(x+α)sin(x−α)dx

=∫sin(x−α+2α)sin(x−α)dx

=∫sin(x−α)cos2αsin(x−α)dx+∫cos(x−α)sin2αsin(x−α)dx

= (x – α) cos 2α + sin 2α log |sin(x – α)| + C