# angle between these two planes

What is the angle between these two planes: x + 2y - z = 13 & -2x - 4y + 2z = -13?

What is the second derivative of f(x, y) = 3x2y + 4y3 first with respect to y and then with respect to x?

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What is the angle between these two planes: x + 2y - z = 13 & -2x - 4y + 2z = -13?

The angle between the two planes is the angle between their normal:

N1= (1, 2, -1), N2= (-2, -4, 2)

N1.N2 = |N1||N2|cos(Ɵ)

cos(Ɵ)= (N1.N2 )/|N1||N2|

Ɵ=cos^(-1)〖((N1.N2 ...

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