Q.

The triangle PQR is inscribed in the circle x2+y2=25. If Q and R have co-ordinates (3, 4) and (-4,3) respectively, then QPR is equal to                 [2000]

1 π2  
2 π3  
3 π4  
4 π6  

Ans.

(3)

O  is the point at centre and P is the point at circumference. Therefore, angle QOR is double the angle QPR.

So, it is sufficient to find the angle QOR. Now slope of OQ=43=m1 (let)

Slope of OR=-34=m2 (let); Now, m1m2=-1

Therefore, QOR=90°     QPR=45°.