Question

What is the area of triangle ABC to the nearest tenth of a square meter?

Answer 1

@whpalmer4

Answer 2

well, what can we conclude about this triangle?

Answer 3

Ohh, I just realized, it's iscoceles (however you spell that)

Answer 4

right.

Answer 5

Oh wait, I think i got it, I find the third side, divide it in half and then I can find the height of the triangle and then the area

Answer 6

well, yes, you can do that. how would you do it?

Answer 7

I use sin(36 degrees)=x/70 and I get 41.145 for the third side, then I divide that by two to get 20.5725 and now I use the pythagorean theorem to find the height

Answer 8

no, it isn't a right triangle, so your trig isn't quite right...

Answer 9

Oh yeah, forgot we can't do trig... what do I do then?

Answer 10

well, we could...you'd bisect that 36 degree angle and make two right triangles. then you could do sin(18 degrees) = (x/2)/70

Answer 11

Another way would be with the law of sines as in the previous problem — because this is an isosceles triangle and we know that the different angle is 36 degrees, we can figure out the two identical angles by subtracting from 180 and dividing by 2

or we could use the side angle side rule for the area of a triangle. that is \(A = s_1 * s_2 * \sin(\theta)\) where \(s1, s2\) are the two sides we know and \(\theta\) is the angle between them.

Answer 12

I use sin(36 degrees)=x/70 and I get 41.145 for the third side, then I divide that by two to get 20.5725 and now I use the pythagorean theorem to find the height

almost.... use the Law of Sines to find the 3rd side

Answer 13

@phi but it's an iscoceles triangle, you can't do sin until u bisect?

Answer 14

no, he was quoting what you said...

Answer 15

Ohh, lol my bad xD

Answer 16

it seemed awefully familiar

Answer 17

palmer's idea is the nicest way... but if you are learning how to use the Law of Sines
you could do this