Machine-translated by Google. Questions are authored in English.
Top

Discussion

In the following diagram, the point R is the center of the circle. The lines PQ and ZV are tangential to the circle. The relation among the areas of the squares, PXWR, RUVZ and SPQT is

Circle with centre R on line TQRZ; square SPQT on the tangent PQ at Q, square PXWR on the segment PR, and square RUVZ on the radii RU and RZ, with ZV tangent at Z

  • A.Area of SPQT = Area of RUVZ = Area of PXWR
  • B.Area of SPQT = Area of PXWR - Area of RUVZ
  • C.Area of PXWR = Area of SPQT - Area of RUVZ
  • D.Area of PXWR = Area of RUVZ - Area of SPQT

Answer: B

The relation is Area of SPQT = Area of PXWR − Area of RUVZ.

PQ is tangent to the circle at Q, so the radius RQ is perpendicular to PQ and triangle PQR is right-angled at Q. By Pythagoras, \(PR^{2} = PQ^{2} + QR^{2}\).

The square PXWR is built on PR, so its area is \(PR^{2}\). The square SPQT is built on PQ, area \(PQ^{2}\). The square RUVZ has sides RU and RZ, both radii, so its area is \(QR^{2}\) (QR is also a radius). Hence

\[ PQ^{2} = PR^{2} - QR^{2} \]

that is SPQT = PXWR − RUVZ. The three areas cannot all be equal, since PR is the hypotenuse and longer than both PQ and QR; the other two options subtract the wrong pair.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.