*<math>tan^2(x)+1 = \frac{sin^2(x)}{cos^2(x)}+1 = \frac{1}{cos^2(x)}</math>
*<math>arctan'(x) = \frac{1}{\frac{1}{cos^2(arctan(x))}} = \frac{1}{tan^2(arctan(x))+1}=\frac{1}{1+x^2}</math>
<videoflash>n9WMYrhb-6I</videoflash>
<videoflash>sryeJtePu_U</videoflash>
==פרק 6 - חקירה==