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**timmyjamesbob****Guest**

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??

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

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:

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**timmyjamesbob****Guest**

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?

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

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 .

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

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

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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