The equation to the lines passing through the origin and inclined at angles π4 and 3π4 to x- axis is
y=tanπ4x, and y=tan3π4x
y=x and y=−x
So, pair of straight line of y=x and y+x=0 is
(y−x)(y+x)=0
⇒y2−x2=0
Or ⇒x2−y2=0
Find the equation of family of circles passing through the point of intersection of the circles x2 + y2 − 2x − 4y − 4 = 0 and x2 + y2 − 10x − 12y + 40 = 0 and whose radius is 4.
A pair of tangents are drawn from the origin to the circle x2+y2+20(x+y)+20=0. The equation of the pair of tangents is