题目

如图，中，，，，则的长为（ ）A. B. C. 5 D. 答案：【答案】C【解析】过C作CD⊥AB于D，根据含30度角的直角三角形求出CD，解直角三角形求出AD，在△BDC中解直角三角形求出BD，相加即可求出答案．过C作CD⊥AB于D，则∠ADC=∠BDC=90，∵∠A=30,AC=，∴CD=AC=,由勾股定理得：AD=CD=3，∵tanB==，∴BD=2，∴AB=2+3=5，故选C. ______, I have never seen anyone who’s as capable as John． A. As long as I have traveled                        B. Now that I have traveled C. As I have traveled so much                      D. Much as I have traveled