using vectors show that the angle in a semicircle is a right angle

## EXPERT ANSWER

Sunanta Achoibam , Meritnation Expert added an answer, on 20/12/10

Hi!

Here is the answer to your question.

Let O (0, 0) be the centre of a semicircle of radius

*a*.The coordinated of any point P on the circle can be written as P (

*a*cos*q*,*a*sin*q*) where*q*is the angle formed by OP with positive direction of*x*-axis.This, means that angle between PA and PB is 90°.

Cheers!

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