bantu jawab no 13 dong kaa

|c| = a . b/ |b|
a . b = (2i -2j +4k) . ( 5i+1j+pk)
=10i -2j +4pk
=10 -2 +4p = 8 +4p
|b| = √5^2 + 1^2 + p^2
=√P^2 + 26

|c| = 8 +4p / √ p^2 +26
4 = 8 +4p / √p^2 +26
4^2 = 16p^2 +64p + 64 / p^2 +26
16( p^2 +26) = 16p^2 + 64p + 64
16p^2 + 416 - 16p^2 - 64p -64 = 0
-64p + 352 = 0
64p - 352 =0
32 ( 2p - 11) =0
2p -11=0
p =11/2 = 5,5