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Problems in Mathematical Analysis.pdf - pwp.net.ipl.pt

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134 Indef<strong>in</strong>ite Integrals_[CH. 4<br />

Transfor Transform<strong>in</strong>g<br />

of squares, t<br />

the quadratic tr<strong>in</strong>omial ax* + bx-\-c <strong>in</strong>to a sum or difference<br />

of squares, the <strong>in</strong>tegral (1) becomes reducible to one of the follow<strong>in</strong>g types<br />

of <strong>in</strong>tegrals:<br />

2) R (z, m* + z*) dz\<br />

3) R (z, Vz 2 m z<br />

) dz.<br />

The latter <strong>in</strong>tegrals are, respectively, taken by means of substitutions:<br />

1) 2 2)<br />

= ms<strong>in</strong>/ or z = m tanh /,<br />

2 3)<br />

= mtan/ or 2 = ms<strong>in</strong>h/,<br />

2 = msec/ or z = m cosh/.<br />

Example 1. F<strong>in</strong>d<br />

Putt<strong>in</strong>g<br />

Solution. We have<br />

(x+\Y<br />

dx<br />

==/.<br />

Putt<strong>in</strong>g *+l = tan2, we then have dx = sec*zdz and<br />

Example<br />

dx f sec 2 zdz f cos 2 .<br />

= \ - = x ~ dz =<br />

tan 2<br />

2. F<strong>in</strong>d<br />

Solution. We have<br />

zsec2~"J

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