Changevar level 1

$val7 .

Changevar level 2

$val7 .

By parts level 1

$val7 .

By parts level 2

$val7 .

Rational level 1

$val7 .

Rational level 2

$val7 .

tg and ctg

$val7 .

Trigonometric level 1

$val7 .