trigonometry HELP PLEASE ASAP?

Question

http://www.revisioncentre.co.uk/gcse/maths/sin_cos_tan.html

could you please look at the example question on that page about it. i know you use cos(angle) = adjacent / hypotenuse
but do you have to use the angle between both sides in this case 60 or could you use any angle opposite in the far corner for instance if it was given to you?

i mean if they gave me the angle in the bottom right or the triangle and not the angle 60 degrees would i still be able to work out the length. do i need to use the angle of 60 degrees or if antother angle was given could i use that instead?

Answer 1

if you want to use cos. you would do cos(60)=x/13 or you could do sin(30)=x/13 your choice (hint with a 30-60-90 triangle the hypoteneuse is twice the side of the short leg)

Answer 2

This is a special triangle having angles of 30,60 and 90 degrees. In such a triangle the shorter leg is equal to 1/2 the hypotenuse. So if hypotenuse = 13, the shorter leg = 6.5
The longer leg is sqrt(3)*shorter leg.

You cold use the 30 degree angle instead of the 60 degree angle, and you would get the same answer.
If you use he 60 degree angle the short leg /hypotenuse = cos 60 . If you use 30 degrees, then short leg /hypotenus = sin 30. You get same answer because sin 30 = cos 60.

Answer 3

You can use the angle on the left as well, and you know its size is 30 degrees (sum of angles in a plane triangle = 180 degrees)

sin 30 = 1/2, and is usually remembered in a trig class

1/2 = x/13
2x = 13
x = 6.5

Answer 4

I can't under stand your question. Cos of any angle may be found. cos = adj side/ hypotenuse. So, if you know that the adjacent side corresponds to that angle, you can find its COS.

Answer 5

No, if they ask for the sin, cos, or tan(or even sec, csc, or cot)of an angle, you must use the angle it is referring to.

Answer 6

Lotta Smart People In Here

Answer 7

better stick with the given (in this case 60). my teacher advised that to our class when we were discussing this topic.