Question

If the sides of a triangle are 4p, 5p and 6p, calculate the size of the lagest angle.

Answer 1

remember the law of sines

your largest angle will be opposite your longest side

and you have a total of 180 degrees to work with

Answer 2

jolly am still lost, pls direct me sir.

Answer 3

forget the p. It is just a scale factor.

using the law of cosines,

6^2 = 4^2 + 5^2 - 2*4*5*cosA
A = 82.82°

Now do a similar equation for B, and then C is easy, since A+B+C=180

Answer 4

sorry Somay - Law of Cosines:

c^2 = a^2 + b^2 – 2ab cosC
where a, b and c are the lengths of the three sides opposite the three angles A, B and C (respectively)

a is the side opposite angle A, etc.

Now let a = 4p and b = 5p and c = 6p

Then you have cosC = – (c^2 – a^2 – b^2)/2ab = – (36 – 16 – 25) / 40 = 1/8 = 0.125
cosC = 82.82 degrees

pls check my algebra in case i made a mistake

Answer 5

okay that's great. Steve thanks a lot

Answer 6

oh okay. Thank you jolly, that's great.