Solution
= Solution
The <trace> sums the diagonal entries, so $\operatorname{tr}P=\sum_i1-\sum_i a_i^2-\sum_i b_i^2$. The two <unit vectors> have squared <Euclidean norms> one, giving $\boxed{\operatorname{tr}P=n-2}$.
= Solution
The <trace> sums the diagonal entries, so $\operatorname{tr}P=\sum_i1-\sum_i a_i^2-\sum_i b_i^2$. The two <unit vectors> have squared <Euclidean norms> one, giving $\boxed{\operatorname{tr}P=n-2}$.