Dear Dad，
   Happy birthday to you !
   On this special day I'd like to talk to you1a special way．
   I don't think I am good at2you my thought face to face with you，so I'm writing to show my deep love for you．You're not a rich man or a famous person．But in my heart，you are one of the greatest3 in the world．I am4 you．
   You are5 interested in fame and wealth．You do6 things like paying phone bills on time，and working as a worker in your factory．The smile on your face shows you are pleased with the family．You take good care of my grandparents．You help me with my schoolwork and do some shopping with Mom on Sundays．
   In the past，I didn't care7 you were with me or not．Now I am sorry to say I8 you the respect before．But I am thankful for what you have done for me． I am quite lucky that I have9 a great father．And I feel happy that now I can let you10 how much I love you．You are successful as a son，a husband，a father，and a friend．
   Wish you happy forever!
                                                                                                                                               Yours，

                                                                                                                                               David

如图，在平面直角坐标系中，点A的坐标为（4，3），那么cosα的值是（  ）

如图，直线a、b都与直线c相交，给出下列条件：①∠1=∠2；②∠3=∠6；③∠4+∠7=180°；④∠5+∠8=180°．其中能判断a∥b的条件是（　　）