How do u find the unknown angle measure in a triangle

Unfortunately, your question is too broad, too vague, for someone to help you.  Could you possibly share a problem in which you have the find the unknown angle measure?

Example:  Supposing you had a right triangle with one of the acute interior angles equal to 30 degrees.  If the hypotenuse is 5 and you are asked to find the length of the opposite side, you'd write this equation:

sin 30 = x/5.  Multiplying both sides by 5, 5 sin 30 = x, or 5(1/2) = x, or x=2 1/2.

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