In 325 AD, Konstantinus the Caesar of Rome lead a Council in Nicaea. One of the result is tofix this calendar problem. He dissapear three days because year range between 325 AD and45 BC are 370 year close to three excess days after the firs leap year in 45 BC. The purposeto let the vernal equinoxes always fall on 21 March, but no decision made to clear thisproblem in the future.Because of that in 1582 AD (1257 year after 325 AD) the spring season shift again almostten days before 21 March. Pope Gregory XIII decided to dissapear 10 days. The day afterWednesday, 4 October 1582 is Friday 15 October 1582. To clear this problem in the future,the Pope with the help from Christopher Clavius (a pastor that expert in astronomy andmathematics) made additional rule to Julian calendar, this called Gregorian Calendar. Theadditional rules are : Every year divisible by 100 is not a leap year but every year divisibleby 400 is a leap year. Example: 1700, 1800, 1900, 2100, 2200, etc are not leap years but1600, 2000, 2400, 2800 are leap year. This rules call Gregorian Calendar. Please note thatyear 1500, 1400, 1300 and on are leap years because the rules work after 1582 AD! This Gregorian Calendar rule fix one additional day every 128 year, but it will have oneadditional day after 3400 years after (because the rate year of Gregorian Calender is365,2242 days, still have a little different with one tropical year), and for our generation nowand our next next next generation it wont be a problem because the problem will occur after3400 year. Some people proposed to fix this 3400 year problem, example Encyclopedia of Britannica suggest to make year 4000 are not a leap year or Delambre (French astronom)suggest to make 3600, 7200, 10800 and so on are not leap years and others suggestion, butuntil now no proposed become a decision. So we are now using Gregorian Calendar after1582 AD and using Julian calendar before 1582 AD.Now what about years before 45 BC? To make everything clear, astronom made a decisionthat Julian Calendar working before 1 AD with the rules the years divisible by 4 is a leapyear, because no 0 AD, then the rules work in astronomical year before 1 AD. What isastronomical year? Its begin with year 0, -1, -2, -3, -4 and on. Year 0 the same with 1 BC,year -1 the same with 2 BC, the year -20 the same with 21 BC. The leap years then are year0 (=1 BC), year -4 (=5 BC), year -8 (=9 BC), year -12 (=13 BC) and on.Back to the question, what number are leap year between 1 Januari 10.000 BC (the samewith year - 9.999) to 31 December 2100 AD? The first leap year between that range is inyear -9996 (or 9997 BC) and the last is 2096 AD, its covers 12.092 years. Divided it with four(the range of leap year) and plus one (because the boundary is leap year), we get 3024. Wehave to minus it because of the Gregorian rule, the year are 1700, 1800 and 1900, thenminus three year, we get 3021.
3.Venus achieves its half phase ata.Superior conjunctionb.Inferior conjunction
c.Maximum West elongation and maximum East elongation
d.retrogradee.Toward superior conjuntion
ANSWER :Venus and Mercury are inferior planets that have phase like the moon, have the crescentphase, full phase or new phase. Superior planet doesn't have this phase, but they haveretrograde motion that inferior planets doesn't. There are four special position of the inferior planets following it's position from the Sun thatsaw on Earth, there are: inferior conjuntion, superior conjunction, greatest west elongationand greatest east elongation. Learn this picture that i take from wikipedia.org:2