Please solve What is the angle of intersection between the c

Please solve!

What is the angle of intersection between the circle x^2 + y^2 = 9 and the circle (x - 5)^2 + y^2 = 16?

Solution

The first is a circle centered 0,0 with radius 3

The second is a circle centered 5,0 with radius 4

Distance between centers is d = 5 { 5-0 = 5}

r1 = 3, r2 = 4

cost = 5^2 - 3^2 -4^2 / 2*4*3 = 0

t = 90 degrees

So, angle between the circles is 90