Math, asked by abhinavsuresh337, 4 months ago

Show that b cos B + c cos C = a cos (B-C).​

Answers

Answered by deepak5780singh
0

Answer:

i don't know had a few days back after school tomorrow

Answered by Anonymous
0

Answer:

It’s not hard to suppose that this identity pertains to a triangle. The Sine Law allows us to say,

asinA=bsinB=csinC=α ,

from which

a=αsinA ,  b=αsinB  and  c=αsinC .

Then the left side becomes

αsinBcosB+αsinCcosC  

=12α[sin2B+sin2C]  

=α[sin(B+C)cos(B−C)]  

=αsin(180−A)cos(B−C)  

=αsinAcos(B−C)  

=acos(B−C

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