Math Is Fun Forum

Kiran

Member

Registered: 2006-11-15

Posts: 177

hi

ok in this i have a problem in my book..which i like for you to help me out with now if you can i will so like that .

ok the top of the obtuse if Mdegrees
the bottom point is 25degrees
and the middle is 125degrees
the hypotenuse is 18
and the opposite side is y
and the ajacent side is x

now i have to find
x
y
Mdegrees

i did
125degrees + 25degrees + Mdegrees = 180
150dg + Mdg = 180
180 - 150 = 30
Mdg = 30dg
right
now how to find y and x?

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Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: hi

You can use the Sine Rule, providing you have learnt it.
(en.wikipedia.com/wiki/sine_rule)
The rule is that one side length over its sine of the opposite angle is proportionate to another side length over the sine of its opposite angle.
Now, I'm assuming the longest side is the hypotenuse and the bottom one is x.

Cross multiply to find x, then repeat for y.

There is another way if you haven't learnt the Sine Rule, but it takes a lot of working:
It is shown in the image attached.
Create an imaginary square around the triangle and fill in all the missing angles, then you can use trigonometry to work out the side lengths.

Last edited by Toast (2006-11-27 17:28:43)

Kiran

Member

Registered: 2006-11-15

Posts: 177

Re: hi

ok so thank you
now the law of sines is
a/sinA
b/sinB
c/sinC
right
now if we want to find y
we have to say
18/sin125 = y/sin(25) ?
for x i got 10.9869713 which is 10.0
now my finding y is that the right way?

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Live 4 Love

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: hi

Yep , and you should probably round 'x' up to 11.

Last edited by Toast (2006-11-28 07:53:56)

WiZaRd

Real Member

Registered: 2006-09-22

Posts: 570

Re: hi

I like to solve Trignomatic Problems Really Interesting

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