In the given circle O is the centre of the circle and AD, AE are the two tangents. BC is also a tangent, then:
2AE = AB + BC + AC
CD = CP and BE = BP, since tangents from the same point are always equal in length.
∴ AE = AD
Now, AD = AC + CD = AC + CP
and AE = AB + BE = AB + BP
∴ AE + AD = AC + CP + AB + BP
2AE = AC + AB + (CP + BP)
2AE = AB + AC + BC