```
180 * subspace(c(1, 2), c(2, 1)) / pi #=> 36.87
180 * subspace(c(0, 1), c(1, 2)) / pi #=> 26.565
H <-
hadamard(8)
A <- H[, 2:4]
B <- H[, 5:8]
subspace(A, B) #=> 1.5708 or pi/2, i.e. A and B are orthogonal
```

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