Một vật dao động điều hòa theo phương trình x = 3cos(2πt - π/3), trong đó x tính bằng xentimét (cm) và t tính bằng giây (s). Hai thời điểm đầu tiên lúc vật có tốc độ cực đại là A. t1 = 1/12 (s), t2 =7/12 (s) B. t1 =5/12 (s), t2 =11/12 (s)
C. t1 =6/12 (s), t2 =2/3 (s) D. t1 =1/3 (s), t2 =11/12 (s)

7. see worksheet 1 for values of variables x1, x2 and x3 and answer the following questions: a. for each variable find the mean, median, coefficient of skewness, range and population standard deviation. b. compared to variable x1, how are the mean and median affected by extreme values (outliers) seen in x2 and x3. c. is the median or mean the better measure of location for x2 and x3? explain. d. explain the differences in the magnitudes of the skewness coefficients for the three variables. e. what is the relationship between the range and standard deviation looking across the three variables?