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1/2ABsinC

Could somebody please explain what 1/2ABsinC is, and how it is used?
Reply 1
Avatar for Malik
Malik
12
It could be used to find the Area of a triangle , where AB are two sides and the angle that joins the two is C.

For an example => http://regentsprep.org/regents/mathb/5E1/areatriglesson.htm
Reply 2
Avatar for yaya1
yaya1
Sorry to bump this thread;

So - 1/2ab would be area of right angles triangle.?

and 1/2absinC would be area of a scalene or isosceles triangle.?
Original post by yaya1
Sorry to bump this thread;

So - 1/2ab would be area of right angles triangle.?

and 1/2absinC would be area of a scalene or isosceles triangle.?


Yes, provided you label your sides correctly, as sin90 = 1.
Reply 4
Avatar for yaya1
yaya1
Original post by marcusmerehay
Yes, provided you label your sides correctly, as sin90 = 1.


'sin90=1' I don't understand this.
Reply 5
Avatar for mjtriggs
mjtriggs
10
Original post by yaya1
'sin90=1' I don't understand this.


Put Sin(90) into your calculator.
Reply 6
Avatar for yaya1
yaya1
Original post by mjtriggs
Put Sin(90) into your calculator.


Yeah but how is that related to the area?
Reply 7
Avatar for mjtriggs
mjtriggs
10
In a right angled triangle, it's equal to 0.5*b*h where b is the base, and h is the height.

In any triangle, the area is 0.5*A*B*SinC. If right-angled, C=90, which is where we get the first formula from.
Original post by yaya1
Yeah but how is that related to the area?


It's more that it's related to SinC. You've got

1/2ab(SinC) (where a and b are two sides, and C is the angle in between them)


You asked about a right angled triangle. Assuming you wanted to know if C is allowed to be a right angle, which is 90, we would write:

1/2ab(Sin90)

We can simplify Sin90 straight away, because it is a number. It equals 1. So you are left with

1/2ab(1) = 1/2ab

I'd just like to note that your question isn't very clear. You've mentioned a right angled triangle (which should be 1/2(base x perpendicular height)), whereas 1/2abSinC works with any angle in a triangle (not just the right angle - it can work with the others provided you have the correct side lengths).
Reply 9
Avatar for yaya1
yaya1
That makes sense
LOOOOOL

Thanks.
Reply 10
Avatar for mcgaw
mcgaw
2
ur welcome haha

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