Let the vectors a, b, c and d be such that (a×b)×(c×d)=0. Let P1 and P2 be planes determined by pair of vectors a, b and c, d respectively. Then the angle between P1 and P2 is

Let the vectors a, b, c and d be such that (a×b)×(c×d)=0. Let P1 a

1.	Let the vectors a, b, c and d be such that (a×b)×(c×d)=0. Let P1 and P2 be planes determined by pair of vectors a, b and c, d respectively. Then the angle between P1 and P2 is
Answer» Let the vectors a, b, c and d be such that $(a \times b) \times (c \times d) = 0$ . Let $P_{1}$ and $P_{2}$ be planes determined by pair of vectors a, b and c, d respectively. Then the angle between $P_{1}$ and $P_{2}$ is