The equation of the circle is x2+y2=4x2+y2=4. Thus, the centre of the circle is (0,0)(0,0) and radius is 2.
Since the line y=x+n⇒x−y+n=0y=x+n⇒x−y+n=0 is a tangent, the perpendicular distance from the point (0,0) to the tangent will be 2.
Thus, we get:
∣∣x−y+n2√∣∣=2|x−y+n2|=2
⇒∣∣0−0+n2√∣∣=2⇒|0−0+n2|=2
⇒n=±22–√⇒n=±22
Thus the two tangent equations are y=x±22–√y=x±22.