In the given figure, find the value of ′a′ is
∠ABP=85(Given)∠AOB=2(∠ABP)(Angleincribedbycentreofcircleisdoubleangleinscribedbyanychord)∠AOB=2×85=170In△AOBSinceOA=OB(Oiscentreofcircle)∠OAB=∠OBA(Anglealongtheequalsideareequal)Hence∠OAB+∠OBA+∠AOB=180∠OAB+∠OBA=180−170=10Hence∠OAB=∠OBA=5∠OAB=a=5Henceoption(D)isthecorrectanswer