Thread: Maths - trigonometry AREA of triangle

1. Maths - trigonometry AREA of triangle

I understand the concept of finding the area:

1/2 x Base x Height Sin(Angle) = Ans

But i don't understand how you reverse the operation to find the Length, such as the image here:

[Q] The area of the triangle ABC is 33.5cm^2.

Calculate the length of BC.

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Please give me the Rule, and how you did it.

2. first of all, you're combining your equations. the area of a triangle in this case is not .5 base x height sin(ang), it's .5 (side a) (side b) sin (ang). to find the side, just plug your values in and you should have only 1 unknown.

I got 10.0087

Work:

area=.5(sidea)(sideb)sin(angle)

sin(73) * 0.5 * 7 * b= 33.5

33.5/sin(73) * 0.5 * 7 =b

b= 10.0087

I think i'm right, check me and let me know if my math is wrong.

3. The Following User Says Thank You to SammyZee56 For This Useful Post:

Para DICE (02-01-2011)

4. You might wanna refresh some of that basic algebra from primary school

5. The Following User Says Thank You to Alen For This Useful Post:

Para DICE (02-01-2011)

6. Originally Posted by Coeus

You might wanna refresh some of that basic algebra from primary school
Primary school? really... damn in the US you learn things early..primary school i was learning my time tables.

7. Originally Posted by Para DICE
Primary school? really... damn in the US you learn things early..primary school i was learning my time tables.
Not the US >_>

And basic algebra (aka a*b=c => a=c/b) is most definitely primary school stuff.

8. Originally Posted by Coeus
Not the US >_>

And basic algebra (aka a*b=c => a=c/b) is most definitely primary school stuff.
Isn't that reverse operation?

9. Originally Posted by Para DICE
Isn't that reverse operation?
Err ... basic algebra? Take a look online, it'll help you probs: Interactive Mathematics - Learn math while you play with it!

10. wait, me? i dont think so. i did put a slash there, just no parentheses. the slash is generally an accepted symbol for division. if i did make a mistake, please be specific so i dont do it in the future. thanks.