题目

When Babbage was working at Cambridge, a new idea occurred to him. He wanted to construct a calculating machine to work out the solutions（解法）to maths problems not only with correctness but also with a speed beyond the power of any human mind. His machine could solve problems involving（涉及）long rows of figures in one continuous operation（运算）.     In 1822 Babbage exhibited his invention and won a prize from the government. After that, he immediately started to work on a larger machine designed to solve more difficult problems. Although he received some money left by hi 在△ABC中，角A，B，C所对应的边分别为a，b，c，且b2＋c2＝bc＋a2，则角A的大小为_________．