Question

in a triangle ABC ,
ANGLE A + ANGLE B = 105 DEGREE
ANGLE B + ANGLE C = 120 DEGREE
find B.

Answer 1

Hi ,

In a triangle sum of the three angles

is equal to 180°.


In triangle ABC ,

A + B + C = 180° -----( 1 )

A + B = 105

A = 105 - B ----( 2 )

B + C = 120°

C = 120 - B -----( 3 )

Put ( 2 ) and ( 3 ) in equation ( 1 ) ,

105 - B + B + 120 - B = 180

225 - B = 180

- B = 180 - 225

-B = -45

Therefore ,

B = 45°

I hope this helps you.

:)

Answer 2

In this triangle,
C + B = 120°.............(i) &
A + B = 105°.............(ii)
We know that in any triangle, A + B + C = 180°.......(iii)
Now, we get from equation (i),(ii),(iii)
A+B+C+B-A-B-C = 120° + 105° - 180°
or, B = 45°




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