Given that length of common chord of two circles =2√17, with same radii one circle is ⇒‌‌x2+y2+6x+4y−12=0 ‌r=√32+22+12=5 both circles have same radii =5
‌AB=2√17 ‌AC=√17 ‌‌ In ‌△AO′C ‌O′C‌=O′A2−AC2 ‌=25−17⇒O′C=2√2 OO′‌=4√2 ⇒‌‌cos‌θ‌=‌