Question

10abc, 2a² + 2abc - 4b²​,i am not getting a write answer

Answer 1

MATHS

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Asked on December 20, 2019 by

Archa Kuruvila

In a triangle ABC, 2a

2

+4b

2

+c

2

=4ab+2ac, then numerical value of cosB is equal to?

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ANSWER

It is given that 2a

2

+4b

2

+c

2

=4ab+2ac

Simplifying, we get

(a

2

−2ac+c

2

)+(a

2

−4ab+4b

2

)=0

(a−c)

2

+(a−2b)

2

=0

a=c and a=2b

Hence

cosB=

2ac

a

2

+c

2

−b

2

=

2a

2

2a

2

−b

2

=

8b

2

8b

2

−b

2

=

8

7

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