`intarctan(4t)dt`
If f(x) and g(x) are differentiable functions, then
`intf(x)g'(x)dx=f(x)g(x)-intf'(x)g(x)dx`
If we write f(x)=u and g'(x)=v, then
`intuvdx=uintvdx-int(u'intvdx)dx`
Using the above integration by parts method,
`intarctan(4t)dt=arctan(4t)*int1dt-int(d/dt(arctan(4t)int1dt)dt`
`=arctan(4t)*t-int(4/((4t)^2+1)*t)dt`
`=tarctan(4t)-4intt/(16t^2+1)dt`
Now let's evaluate `intt/(16t^2+1)dt` by using the method of substitution,
Substitute `x=16t^2+1,=>dx=32tdt`
`intt/(16t^2+1)dt=intdx/(32x)`
`=1/32ln|x|`
substitute back `x=16t^2+1`
`=1/32ln|16t^2+1|`
`intarctan(4t)=t*arctan(4t)-4/32ln|16t^2+1|+C`
`intarctan(4t)=t*arctan(4t)-1/8ln|16t^2+1|+C`
C is a constant.
`intarctan(4t)dt`
If f(x) and g(x) are differentiable functions, then
`intf(x)g'(x)dx=f(x)g(x)-intf'(x)g(x)dx`
If we write f(x)=u and g'(x)=v, then
`intuvdx=uintvdx-int(u'intvdx)dx`
Using the above integration by parts method,
`intarctan(4t)dt=arctan(4t)*int1dt-int(d/dt(arctan(4t)int1dt)dt`
`=arctan(4t)*t-int(4/((4t)^2+1)*t)dt`
`=tarctan(4t)-4intt/(16t^2+1)dt`
Now let's evaluate `intt/(16t^2+1)dt` by using the method of substitution,
Substitute `x=16t^2+1,=>dx=32tdt`
`intt/(16t^2+1)dt=intdx/(32x)`
`=1/32ln|x|`
substitute back `x=16t^2+1`
`=1/32ln|16t^2+1|`
`intarctan(4t)=t*arctan(4t)-4/32ln|16t^2+1|+C`
`intarctan(4t)=t*arctan(4t)-1/8ln|16t^2+1|+C`
C is a constant.
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