Q2 of 14 Page 77

Let’s try to write the measurement of the angles from the figure given below:


TOS=20°
POQ=60°
POT=?
ROP=?
QOS=?


In the above given figure, let us understand the pairs of vertically opposite angle.

ROQ is lying opposite to POS.


So, our first pair of vertically opposite angles is ROQ and POS.


ROP is lying opposite to QOS.


So, our second pair of vertically opposite angles is ROP and QOS.


Vertically opposite angles are equal.


So ROQ = POS


and ROP = QOS.


Sum of all vertically opposite angles is 360°.


ROQ + POS + ROP + QOS = 360°.


Now in the above question,


POS = POT + TOS


ROQ = 60°.


TOS = 20°


So POS = ROQ = 60°.


POT = POS - TOS


= 60 – 20


= 40°.


Let ROP = QOS = x [as QOS = ROP……… vertically opposite angles]


So, 60° + 60° + x + x = 360°


120° + 2x = 360°


2x = 360 – 120


2x = 240


x = 240 / 2


x = 120°


So QOS = ROP = 120°.


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