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9. What is the size of the ∠POQ where O is the centre of the circle?9. What is the size of the ∠POQ where O is the centre of the circle? |
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Answer» Answer: GIVEN that, O is the centre of a circle, PQ is a chord and the TANGENT PR at P makes an angle of 50 o with PQ. We need to find ∠POQ. We KNOW that the tangent is PERPENDICULAR to the radius. ∴∠OPQ+∠QPR=90 o From the figure ∠QPR=50 o . ⇒∠OPQ+50 o =90 o ⇒∠OPQ=90 o −50 o ∴∠OPQ=40 o We know that, the angles opposite to the equal sides of the triangle are equal. ∴∠OPQ=∠OQP=40 o Also, we know that sum of angles in the triangle is 180 o . ⇒∠OPQ+∠OQP+∠POQ=180 o ⇒40 o +40 o +∠POQ=180 o ⇒80 o +∠POQ=180 o ⇒∠POQ=180 o −80 o ∴∠POQ=100 |
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