完成作业3-2-1

2509165016-3.py

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+import math
+
+A = [3, 4]
+B = [1, 2]
+
+# 1. A + B
+add_result = [a + b for a, b in zip(A, B)]
+print("A + B =", add_result)
+
+# 2. 2 × A
+scalar_result = [2 * a for a in A]
+print("2 × A =", scalar_result)
+
+# 3. A的长度
+norm = math.sqrt(sum(a**2 for a in A))
+print("A的长度 =", norm)

2509165016-4.py

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+import math
+
+def cosine_similarity(a, b):
+    dot = sum(x * y for x, y in zip(a, b))
+    norm_a = math.sqrt(sum(x**2 for x in a))
+    norm_b = math.sqrt(sum(x**2 for x in b))
+    return dot / (norm_a * norm_b)
+
+# 题目4-1,4-2
+A = [1, 2, 3]
+B = [4, 5, 6]
+dot_product = sum(a*b for a,b in zip(A,B))
+print("点积 =", dot_product)
+print("余弦相似度 =", cosine_similarity(A, B))
+
+# 题目4-3
+A2 = [1, 0]
+B2 = [0, 1]
+print("特殊向量余弦相似度 =", cosine_similarity(A2, B2))