Question

plz answer this question​

Answer 1

Step-by-step explanation:

|1 = |2 and |3 = |4 ....................1

in ∆ ABC , A + B + C = 180°. [ angle sum property ]

=> A + 1+2+3+4 = 180°

=> A + 2|2 + 2|4 = 180° [ from equation 1 ]

=> 2 [ |2 + |4 ] = 180° - A

=> |2 + |4 = (180 - A)/2 = 90° - A/2 .............2

in ∆ OBC, |O = 180° - ( |2 + |4 )

=> |O = 180° - [ 90° - A/2 ] [ from equation 2 ]

=> |O = 180° - 90° + A/2

=> |O = 90° + A/2 hence proved