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#1 2006-08-30 08:13:05

timmyjamesbob
Guest

Trig

Can some one help me here im doin some trig and ive no idea how to work out the angle marked x ok im given 2 sides the opposite and hypotinuse no angles are given, how do i work this out??

#2 2006-08-30 08:36:52

Zhylliolom
Real Member
Registered: 2005-09-05
Posts: 412

Re: Trig

Since sin x = opposite/hypotenuse, you can figure out the angle as x = sin-¹(opposite/hypotenuse).

Do you know about sin-¹?

This page may be helpful with some trigonometry, if you forget what each trigonometric ratio is:

http://www.mathsisfun.com/sine-cosine-tangent.html

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#3 2006-08-30 08:40:42

timmyjamesbob
Guest

Re: Trig

hmm i know that thats inverse sine but apart form that i have no idea what it means.
u can find out angles with that yeah?

#4 2006-08-30 09:00:59

Zhylliolom
Real Member
Registered: 2005-09-05
Posts: 412

Re: Trig

Yes. For example, if our angle is y and the opposite side is 1 and the hypotenuse is 2, then sin y = 1/2 and y = sin-¹(1/2) = 30°. You might need a table of values for inverse trigonometric ratios or a calculator. After a while you'll start to memorize some of the values though smile.

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#5 2006-08-30 09:26:41

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

Re: Trig

A little more detailed version:

The inverse sin function is defined in such a way so that:

sin-¹(sin(x)) = x

So:

sin(y) = 1/2
sin-¹(sin(y)) = sin-¹(1/2)
y = sin-¹(1/2)


"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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#6 2006-08-30 18:31:24

Devantè
Real Member
Registered: 2006-07-14
Posts: 6,400

Re: Trig

timmyjamesbob wrote:

hmm i know that thats inverse sine but apart form that i have no idea what it means.
u can find out angles with that yeah?

And if you need any practice, just try this exercise: http://www.mathsisfun.com/forum/viewtopic.php?id=4213

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