Yeah it is a straight line so you can say it's 180 deg or you can prove b to he 70 deg (Vertically opposite) and this 2a = 360-140=220, a=110When describing angle 'a', is a reasoning of 'Supplementary angle' a good enough reasoning when putting in an explanation?
e.g
 or (Supplementary angle adds up to 180^\circ) $ )
Best way of saying it is adjacent supplementaryWhen describing angle 'a', is a reasoning of 'Supplementary angle' a good enough reasoning when putting in an explanation?
e.g
If you take a common denominator, your answer will simplify to the book's one.
I didn't quite get the last part, part (d)
I had something along the lines of E=180-I
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No, congruency for shapes with more than 3 sides becomes more complicated. Like a simple example, a square has the same side lengths as a rhombus formed with equal side lengths, but these shapes are not congruent, despite an 'SSSS'. (Similar things occur for shapes with 5 sides or more.)
I just noticed in the Cambridge Year 10 text book, they did congruency tests for quadrilateral shapes. But what they do is they divide it up into two triangles so that you can do your further tests.
Yeah, there are congruency tests for higher-sided polygons, it's just that they're going to be more complicated (or less practical to apply) than the standard triangle ones (like for quadrilaterals, the Cambridge Year 10 book is reducing it to the case of triangles, because triangles are really the only simple one). If you're curious, you can find out some more about congruency for general polygons here: http://www.mathopenref.com/congruentpolygonstests.html . But congruency tests for higher-sided polygons isn't tested in the HSC I believe.
I don't know how strict the HSC is on such things, but it is generally a bad idea to state congruences and similarities without listing the vertices in order of their correspondence (which is not the case with your statement, the angles are not in the same order).
In the books answer it said :
Could I have also said:
?