2013年高考新课标Ⅰ卷第17题的得分率比较低,笔者刚看这个题目时,感觉题目不是很难,而高考评卷过后,发现该题的得分率确实不高。对于这样一个中档题目,命题人的目的应该是考查学生对三角函数以及解三角形方面的知识掌握情况,应该算是中档题目,下面通过对该题目进行深度解读,以便对正在复习备考的同学有一定的帮助。题目如图1,在△ABC中,∠ABC=90°,AB=3~(1/2),BC=1,P为△ABC内一点,∠BPC=90°。(1)若BP=1/2,求PA; 2013 college entrance examination new curricula Ⅰ Volume 17 score rate is relatively low, I just look at this topic, the feeling of the problem is not difficult, but after the entrance examination marking, found that the problem score is indeed not high. For such a mid-range title, the purpose of the proposition should be to examine students’ knowledge of trigonometric functions and solving triangles should be considered mid-range title, the following through the depth interpretation of the subject, so that students are reviewing the preparation of a certain degree of help. The problem is shown in Figure 1, △ ABC, ∠ABC = 90 °, AB = 3 ~ (1/2), BC = 1, P for △ ABC within a point, ∠ BPC = 90 °. (1) If BP = 1/2, find PA;