CIRCLE

1>Find the equations of the tangents from the point B(3,8) to the circle x^2+y^2-4x-16=0.

2>Find the equations of the tangents to the circle x^2+y^2=4 which are perpendicular to the line x+y=1.

3>Find the equations of the tangent to the circle x^2+y^2+6x-2y+5=0 which are parallel to the line 2x+y+3=0.

4>If the line 3x-4y+k=0 is tangent to the circle x^2+y^2=25, find the values of k.