18.1  a) integrate 2x^2+1 dx from -3 to 2
      b) integrate (x+5)/(x^2) dx from -5 to -1
      d) integrate sin^2(x/2) dx from -pi/2 to pi/2
      e) integrate ((sin (2x))^3)/((cos x)^3) from -pi/3 to pi/3

18.2  b) integral |2-x| dx x from 0 to 4 
      c) integral |x^2-2x| dx x from -1 to 3
      d) integral sqrt(1-sin^2x) dx x from -pi to pi/2
      e) integral x*sqrt(x^2-1)^2 dx where x from -1 to 2
      f) integral |x^2+2x-3| dx x from -5 to 3

18.3  a) integral (8x^2020 + sin x) dx where x from -1 to 1
      b) integral (x^4-cos x) dx from -pi to pi
      c) integral 5x/(4+x^2)^2 from -1 to 1

18.4  b) integral 1/(3x+4) dx where x from -1 to 1
      c) integral x*sqrt(x^2+1) dx where x from 0 to 3
      d) integral x^3*(2x^4-5)^6 dx where x from -1 to 1
         1/8*(2x^4-5)^7/7 - integral x^3*(2x^4-5)^6 dx
      e) integral |ln 5x|/x dx from 0.1 to e
         1/2*(ln^2(5e)+ln^2 2) - (integral (ln 5x)/x dx where x from 0.2 to e) + (integral (ln 5x)/x dx where x from 0.1 to 0.2)
      g) integral 1/(x^2+2x+2) dx x from -1 to 0
      h) integral sqrt(x)/(1+sqrt(x)) dx x from 0 to 1

18.5  a) integral x^2/(x+1)^4 dx x from 0 to 1
      b) integral x/(sqrt(1+3x)) dx x from 0 to 5
      c) integral sqrt(1-x^2) dx x from -1 to 1

18.6  a) integral 1 dx from -1 to 0 + integral sqrt(x) dx from 0 to 1
      b) integral 1/cos^2x dx from 0 to pi/4 + integral 1/sin^2x dx from pi/4 to pi/2