Eric Nicholas K's answer to LockB's Secondary 3 A Maths Singapore question.
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This is the cosine rule, which you will learn together with the sine rule. The two formulae are used to find lengths or angles in any triangle, not just right angled ones.
Having said that, I believe that the question wants you to put x = 78, since you have not learnt cosine rule but you have learnt similar triangles.
Having said that, I believe that the question wants you to put x = 78, since you have not learnt cosine rule but you have learnt similar triangles.
Date Posted:
3 years ago
a and b is no longer the hypotenuse and adjacent line of the triangle as there is no more right angle?
For right angled triangles where you pick one of the non-right angled triangles, you have one opposite and two adjacents, correct?
(Adjacent means “to the side”)
One of the adjacents will be the longest length of the triangle and it’s called the hypotenuse. The other is just an ordinary adjacent. Correct?
With a non-right angled triangle, the two adjacents are just ordinary adjacents.
(Adjacent means “to the side”)
One of the adjacents will be the longest length of the triangle and it’s called the hypotenuse. The other is just an ordinary adjacent. Correct?
With a non-right angled triangle, the two adjacents are just ordinary adjacents.
does that mean we can randomly pick one of the 2 lines to be a and b, like theres no fixed line to be a and to be b
The a and b can be any of the two adjacent sides, but the c must be strictly the opposite, in the formula
c2 = a2 + b2 - 2ab cos C
But if your school teaches you
a2 = b2 + c2 - 2bc cos A
instead, then the “a” is the one in the opposite
c2 = a2 + b2 - 2ab cos C
But if your school teaches you
a2 = b2 + c2 - 2bc cos A
instead, then the “a” is the one in the opposite
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