Diketahui vektor u = (−1, −1, r), v = (−r, r, 2), dan sudut antara kedua vektor

Jawaban:

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Penjelasan dengan langkah-langkah:

cos a = u . v / |u| . |v|

|u| = √[(-1)² + (-1)² + r²]

|u| = √[2 + r²]

|v| = √[(-r)² + r² + 2²]

|v| = √[2r² + 4]

u . v = (-1 . -r) + (-1 . r) + (r . 2)

u . v = 2r

cos 120 = 2r / √[2 + r²] √[2r² + 4]

-1/2 = 2r / √[2 + r²] √[2r² + 4]

r = -√2

2r² – 5

2(-√2)² – 5

2 . 2 – 5

4 – 5

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