下面是2013年1月28日的SAT官方每日一题的内容，是关于数学方面的，题型是选择。SAT官方每日一题是collegeboard每天都会发布的题目，关于SAT考试的三个部分的各个题型。下面我们就一起来看一下这个SAT官方每日一题吧。

　　SAT官方每日一题之数学---选择：

　　Mathematics > Standard Multiple Choice

　　Read the following SAT test question and then click on a button to select your answer.

　　If the functionis defined by, where, for which of the following values ofisundefined?

　　(A) None

　　(B)only

　　(C)only

　　(D)andonly

　　(E),, and

　　The correct answer is C

　　Explanation

　　If, then. If, then. If, then, which is not defined because division byis undefined. Therefore, of the three values,,, and, the only one for whichis undefined is. Thus the correct response isonly.

　　下面是一道和SAT官方每日一题相似的题目，供大家练习：

　　The stopping distance of a car is the number of feet that the car travels after the driver starts applying the brakes. The stopping distance of a certain car is directly proportional to the square of the speed of the car, in miles per hour, at the time the brakes are first applied. If the car’s stopping distance for an initial speed of miles per hour is feet, what is its stopping distance for an initial speed of miles per hour? 

　　Answer Choices

　　(A) feet 

　　(B) feet 

　　(C) feet 

　　(D) feet 

　　(E) feet 

　　The correct answer is D

　　Explanation

　　The stopping distance is directly proportional to the square of the initial speed of the car. If represents the initial speed of the car, in miles per hour, and represents the stopping distance, you have that the stopping distance is a function of and that , where is a constant. Since the car’s stopping distance is feet for an initial speed of miles per hour, you know that . Therefore, , and the car's stopping distance for an initial speed of miles per hour is feet. 

　　以上就是关于2013年1月28日SAT官方每日一题中数学部分的详细内容，包括了题目和选项以及答案，后面附有一道相关的练习题。大家可以在备考SAT的过程中关注SAT每日一题的内容，这样就可以更好有不间断的练习，也就能在日积月累的过程中得到提高。