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secondary 3 | A Maths
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can someone explain what is going on here? why is 148.51 rejected
Date Posted: 4 years ago
Views: 281
Because 148 + 47 = 195 and this would have exceeded the maximum allowable total sum of the angle.
there are 2 types of ambiguous case tho
1 of them can have both angles as answer and for this have to reject one
what is the difference between them and how to know which one to use? im very confused about ambiguous case
1 of them can have both angles as answer and for this have to reject one
what is the difference between them and how to know which one to use? im very confused about ambiguous case
Actually, as long as you use the sine rule to find an angle, you have to classify every single possibility as x and 180 - x as per what I have explained over the past days.
From there, we see whether both cases are valid or we have to reject one of them. The ambiguity arises when both cases are actually possible and will lead to two very different diagrams.
We see whether each case is accepted or not. For example, in this question, accepting 148 would mean that 148 + 47 = 195 which would exceed 180 and therefore would not make sense, so we have to reject it.
From there, we see whether both cases are valid or we have to reject one of them. The ambiguity arises when both cases are actually possible and will lead to two very different diagrams.
We see whether each case is accepted or not. For example, in this question, accepting 148 would mean that 148 + 47 = 195 which would exceed 180 and therefore would not make sense, so we have to reject it.
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Hope this helps. Let me know if you still have any clarification! Good luck
Date Posted:
4 years ago
Not true. I’m pretty sure my eyes tell me that one of the angles is obtuse.
Nevertheless, substitution back into the triangle to check whether the sum of two angles exceed 180 degrees or not is necessary for such questions.
Nevertheless, substitution back into the triangle to check whether the sum of two angles exceed 180 degrees or not is necessary for such questions.
Agree with Eric, that would be a better way to do it. Thanks
thx :)
when we use the sine rule do we always have to do sin-1(angle) or 180-sin-1(angle) when we want to find angle or does it depends on the situation whether we should do both or just the sin-1(angle)
To play safe, do both all the time if the other given angle is lower than 90.
(If the angle given is more than 90, our wanted angle cannot be obtuse already).
That said, from my experience, quite often it happens that if the other given angle is 60, then our wanted angle is usually acute. But to play safe, do both.
The smaller the other given angle, the more likely the obtuse case is possible.
(If the angle given is more than 90, our wanted angle cannot be obtuse already).
That said, from my experience, quite often it happens that if the other given angle is 60, then our wanted angle is usually acute. But to play safe, do both.
The smaller the other given angle, the more likely the obtuse case is possible.
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