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The quadratic (in cot) is a "u" and cuts the y axis at -5 so there are two solutions (for cot). As the linear term/gradient is fairly small at that point (-1) the roots will be roughly symmetric about 0.
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So you have a positive and negative root for tan (1/cot) and therefore the corresponding angles will be roughly equal about 0 so about +/-30. arctan returns values in the range -90..90.
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Those are the two principle values and tan repeats every 180 so as they want solutions in -180 to 180, then 30 and 30-180 and for the other root gives -30 and -30+180.
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If there are two roots for the original quadratic, then you will get 4 angles in the range -180..180 as each root will correspond to two angles.
•
The quadratic (in cot) is a "u" and cuts the y axis at -5 so there are two solutions (for cot). As the linear term/gradient is fairly small at that point (-1) the roots will be roughly symmetric about 0.
•
So you have a positive and negative root for tan (1/cot) and therefore the corresponding angles will be roughly equal about 0 so about +/-30. arctan returns values in the range -90..90.
•
Those are the two principle values and tan repeats every 180 so as they want solutions in -180 to 180, then 30 and 30-180 and for the other root gives -30 and -30+180.
•
If there are two roots for the original quadratic, then you will get 4 angles in the range -180..180 as each root will correspond to two angles.
Last reply 5 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
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Last reply 5 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
Edexcel A Level Mathematics Paper 2 unofficial mark scheme correct me if wrong71