为迎接***建党90周年，某校举办“红歌伴我成长”歌咏比赛活动，参赛同学的成绩分别绘制成频数分布表和频数分布直方图（均不完整）如下：

（1）求m，n的值分别是多少；

（2）请在图中补全频数分布直方图；

（3）比赛成绩的中位数落在哪个分数段？

已知sin（π+θ）=$\frac{1}{2}$，求$\frac{\cos \left(3\mathrm{\pi }+\mathrm{\theta }\right)}{\cos \cos \left(\pi -\theta \right)-1}$+$\frac{\cos \left(\theta -2\pi \right)}{\sin \left(\theta -\frac{7\pi }{2}\right)\cos \left(\pi -\theta \right)-\sin \left(\frac{3\pi }{2}+\theta \right)}$的值．

    Li Qinmei lives in Zhucheng, Shandong Province. She lost her 1 at three. Four years later, her father couldn't 2 after an accident. After the death of her grandmother, 12-year-old Li Qinmei had to support her broken family.

    Qinmei learnt to 3 and live a life with 24 yuan per month from the government. The most 4 things she had to deal with were to 5 her father wash, dress and use the toilet as he could hardly move.

    During most of her junior school years, she went to classes 6 once a month as her father was seriously ill at that time. “I taught 7 at home and asked teachers for help on my school days,” she said.

    Though she had a hard life, the difficulties taught her to be 8. “My classmates have both Mum and Dad to 9 them. How happy they are! However, I don't feel 10 as I still have my dear dad and many kind people with me. I believe I will go to college,” she said.

分子式为C₅H₁₀O₂的有机物在酸性条件下可水解为酸和醇，若不考虑立体异构，这些酸和醇重新组合可形成的酯共有（　　）