The Total solution for NCERT class 6-12
╬ФABC is an isosceles triangle in which AB = AC. Side BA isproduced to D such that AD = AB (see the given figure). Show that тИаBCD is a right angle.
In ╬ФABC,
AB = AC (Given)
тЗТ тИаACB = тИаABC (Angles opposite to equal sides of atriangle are also equal)
In ╬ФACD,
AC = AD
тЗТ тИаADC = тИаACD (Angles opposite to equal sides of atriangle are also equal)
In ╬ФBCD,
тИаABC + тИаBCD + тИаADC = 180┬║(Angle sum property of a triangle)
тЗТ тИаACB + тИаACB +тИаACD + тИаACD = 180┬║
тЗТ 2(тИаACB + тИаACD) = 180┬║
тЗТ 2(тИаBCD) = 180┬║
тЗТ тИаBCD = 90┬║