Find the angle to intersection of the following curves :

y = x2 and x2 + y2 = 20

Given:


Curves y = x2 ...(1)


& x2 + y2 = 20 ...(2)


First curve y = x2


m1 = 2x ...(3)


Second curve is x2 + y2 = 20


Differentiating above w.r.t x,


2x + 2y. = 0


y. = – x


m2 ...(4)


Substituting (1) in (2),we get


y + y2 = 20


y2 + y – 20 = 0


We will use factorization method to solve the above Quadratic equation


y2 + 5y – 4y – 20 = 0


y(y + 5) – 4(y + 5) = 0


(y + 5)(y – 4) = 0


y = – 5 & y = 4


Substituting y = – 5 & y = 4 in (1) in (2),


y = x2


when y = – 5,


– 5 = x2


x


when y = 4,


4 = x2


x = ±2


Substituting above values for m1 & m2,we get,


when x = 2,


m14


when x = 1,


m14


Values of m1 is 4 & – 4


when y = 4 & x = 2


m2


when y = 4 & x = – 2


m2


Values of m2 is &


when m1 = ∞ & m2 = 0



tanθ


tanθ


tanθ


θ = tan – 1()


θ77.47


1