In the path of Mars against the background stars shown in Figure 2-2, the planet appears from Earth to move in a loop, moving westward for a period of time. In the 2012 loop, what is the angle between the Earth-Sun line and Earth-Mars line when the planet is halfway through the retrograde motion, in late February? 
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A company or entity involved in the production of calculators, ranging from basic to advanced scientific and graphing models.
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