Question

Show that cos A + cos B + cos C = 1 +
R​

Answer 1

Answer:

Step-by-step explanation:

cosA+cosB+cosC

=1+4sin(  

2

A

​  

)sin(  

2

B

​  

)sin(  

2

C

​  

)

=1+  

R

(4Rsin(  

2

A

​  

)sin(  

2

B

​  

)sin(  

2

C

​  

))

​  

 

=1+  

R

r

​  

Answer 2

Step-by-step explanation:

cosA+cosB+cosC

1+4sin(A/2)*sin(B/2)*sin(C/2)

1+[4rsin(A/2)*sin(B/2)*sin(C/2)]/R

1+r/R