Given radius =2cm Therefore AO=2cm Let OD be the perpendicular from O on AB And AB =2cm Therefore AD=1cm (perpendicular from the centre bisects the chord) Now in triangle AOD, AO=2cm AD=1cm And let angle AOD =θ Therefore , sinθ=21Hence, θ=45o Therefore angle AOB =45o+45o=90o Then angle APB =290=45o {angle made by a chord at the centre is double of the angle made by the chord at any poin on the circumference)