（Ⅰ）求角C的大小；

（Ⅱ）若a= $\sqrt{2}$ ，c=1，求△ABC的面积．

    Chinese students always complain that they're under great pressure and don't get enough sleep. But they may be surprised to learn that they're much luckier than their peers (同龄人) in South Korea and Japan, according to a recently published report, conducted by Shanghai Academy of Social Sciences on the physical and mental health of senior high school students in the three Asian countries.

    According to the study among nearly 6,000 high school students in the three countries, Chinese students are the tallest but poorest in physical fitness. Chinese students are on average 168.17cm, compared with 167.61cm for South Korean students and 164.70cm for Japanese students. Chinese students asked for sick leave more than students in other countries. About 72 percent of Korean students never asked for sick and injury leave during high school, compared to 53 percent for Japanese students and 45 percent for Chinese students. Moreover, Chinese students drink alcohol and smoke earlier than Korean and Japanese students. Around 70 percent of Chinese students have drunk alcohol, compared to 50 percent for Korean and Japanese students.

    According to the survey, Japanese and South Korean students suffer more pressure than their Chinese peers. Statistics (统计) show 16 percent of students in China said they experienced mental pressure often over the past year, while the numbers in Japan and South Korea were 33 percent and 47 percent respectively. Their worries come from “study”, “future after graduation”, “friendships” and “relationship with their parents”. To go with stress, 57.9 percent of Korean students sleep the least, less than six hours a day, compared with 46.6 percent of Japanese students and 30 percent of Chinese students.

    More Chinese students were satisfied with their physical appearance, double that of students in the survey from Japan and South Korea. The report said that over half of students in South Korea had tried to lose weight in the past year, while in China the figure was only 22 percent.

    In measures of self-worth, such as “I think I am valuable” and “I think I am successful”, “I can complete many things”, “I won't give up to failure,” Chinese students showed greater self-confidence than students in Japan and South Korea.

阅读材料，回答问题。

材料一：由于中国人闭关自守，骄傲自满，三次灾难性的战争使他们受到了巨大的刺激。第一次是同英国的战争，第二次是同英、法的战争，第三次是同日本的战争。这些战争迫使中国人打开大门，结束他们对西方的屈尊态度，重新评价自己的传统文明。              ——摘自《全球通史》

材料二：外侮日深，国家益趋危殆……国民今日皆已深切感觉存则俱存，亡俱亡之意义……此次***发表之宣言，即为民族意识胜过一切之例证……在存亡危急之秋，更不应计较过去之一切……必集中整个民族力量，自卫自助，以抵暴敌，挽救危亡。

——1937年9月蒋介石对中共宣言的谈话