The ΔPQR is inscribed in the circlex2+y2=25 . If Q andR  have coordinates (3, 4) and(−4, 3)  respectively, then ∠QPR is equal to

Ans:3Let m1=slopeof OQ=43 and m2=slopeof OR=−34.As m1m2=−1,  R(−4,3)∠QOR=π2Thus,∠QOR=π4(∵ angle subtended at the centre of a circle is doubledthe angle subtendedin the alternate segment)