The pythagorean theorem is
[tex]c^2=a^2+b^2[/tex]
Note that in unit circle, the radius is 1 and it also represents the hypotenuse in a right triangle.
From the problem :
[tex]\sin \theta=\frac{3}{5}\quad \cos \theta=\frac{4}{5}[/tex]
This will be the a and b in the pythagorean theorem.
It will be :
[tex](\frac{3}{5})^2+(\frac{4}{5})^2=1[/tex]
The answer is B.
