Recall the definition of the cross product:
i x i = j x j = k x k = 0
i x j = k
j x k = i
k x i = j
The cross product is antisymmetric, or anticommutative, meaning that for any vectors u and v, we have u x v = - (v x u).
It's also distributive, so for any vectors u, v, and w, we have (u + v) x w = (u x w) + (v x w).
Taking all of these properties together, we get
b x a = (6i - j + 2k) x (2i + 2j - 5k)
b x a = 12 (i x i) - 2 (j x i) + 4 (k x i)
............. + 12 (i x j) - 2 (j x j) + 4 (k x j)
............. - 30 (i x k) + 5 (j x k) - 10 (k x k)
b x a = 1 (j x k) + 34 (k x i) + 14 (i x j)
b x a = i + 34j + 14k
Answer:
The amount of weight he has lost in 3 months is 1.215 stone or 1 stone 3 pounds
Step-by-step explanation:
From the above question, we are to calculate the amount of weight he has lost in three months
1 stone = 14 pounds
Let's convert all the weight lost to stone
At the start of the diet keirin weighted 14 stone 13 pounds
14 pounds = 1 stone
13 pounds = x
Cross Multiply
14x = 13
x = 13/14
x = 0.9285714286 stone
Approximately = 0.929 stone
Hence:
14 stone 13 pounds = 14 + 0.929 = 14.929 stone
Three months later he weighted 13 stone 10 pounds
14 pounds = 1 stone
10pounds = x
Cross Multiply
14x = 10
x = 10/14
x = 0.7142857143 stone
Approximately = 0.714 stone
Hence:
13 stone 10 pounds = 13 + 0.714 = 13.714 stone
The amount of weight he has lost is calculated as:
14.929 stone - 13.714 stone = 1.215 stone or 1 stone 3 pounds
