o = 4 . a

S = a . v_a

S = 4 . a

o = a + b + c + d

S = a . a

S = a . b

o = a . a

o = 4 . a

o = 4 . a

S = b . v_b

S = a . b

o = 2.a + 2.b

o = 2 . (a + b)

S = a . v_a

S = b . v_b

S = a . b

S = a . a

o = 2.a + 2.b

$S\ =\ \frac{a\ .\ v_a}{2}$

$S\ =\ \frac{b\ .\ v_b}{2}$

$S\ =\ \frac{c\ .\ v_c}{2}$

$S\ =\ \frac{b\ .\ v_c}{2}$

$S\ =\ \frac{a\ .\ v_b}{2}$

o = 4 . a

S = a . a

S = a . b

o = 2.a + 2.b

S = a . v_a

S = a . a

o = 4 . a

o = a . v_a

o = a + b + c + d

o = 4 . a

o = a . b

o = 2.a + 2.b

o = 2 . (a + b)

$S\ =\ \frac{a\ .\ v_a}{2}$

o = 4 . a

o = 3 . b

o = a + b + c

 $S\ =\ \frac{a\ .\ b\ .\ c}{2}$  

 $S\ =\ \frac{a\ .\ b}{2}$  

 $S\ =\ \frac{a\ +b\ +\ c\ }{3}$  

 $S\ =\ a\ +\ v_a$  

o = a + b + c + d

o = a + b + c

o = a . b . c . d

o = 2.(a + b + c + d)

 $S\ =\ \frac{a\ .\ b\ .\ c}{2}$  

 $S\ =\ \frac{\left(a\ +\ c\right)\ .\ v}{2}$  

 $S\ =\ \frac{a\ +b\ +\ v}{2}$  

 $S\ =\ \frac{\left(a\ +b\right).\ c}{2}$