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Use the vectors to determine two dot products: u•v and u•w
u=9i-6j
v=-3i-2j
w=19i+15j


Use The Vectors To Determine Two Dot Products Uv And Uw U9i6j V3i2j W19i15j class=

Sagot :

A

Take the product of corresponding components, then take the total:

u • v = (9i - 6j) • (-3i - 2j) = 9 (-3) + (-6) (-2) = -15

u • w = (9i - 6j) • (19i + 15j) = 9 × 19 + (-6) 15 = 81

Alternatively, use the definition and algebraic properties of the dot product.

• For any vector x,

x • x = ||x||²

where ||x|| is the magnitude of x.

• i • i = j • j = k • k = 1

• i • j = j • k = k • i = 0

• For any scalar c and any two vectors x and y,

cx • y = x • cy = c (x • y)

• For any vectors x, y, and z,

(x + y) • z = z • (x + y) = x • z + y • z

Then the products you want are

u • v = (9i - 6j) • (-3i - 2j)

… = -27 (i • i) + 18 (j • i) - 18 (i • j) + 12 (j • j)

… = -27 + 12 = -15

u • w = (9i - 6j) • (19i + 15j)

… = 171 (i • i) - 114 (j • i) + 135 (i • j) - 90 (j • j)

… = 171 - 90 = 81