document.write( "Question 494689: I have 3 side measures given to me, but how do I use trig to find the angle measures? \n" ); document.write( "

Algebra.Com's Answer #335904 by cleomenius(959) $\"\"$ $\"About$

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If this is a right triangle, you can use the tangent function, tan angle = opp/adj.
\n" ); document.write( "Once you have one angle, you can use the law of sines to find another angle.
\n" ); document.write( "sin A/ side A = Sin B/ side b.
\n" ); document.write( "Once you have the measure of two angles, you can find the remaining angle by adding the two and subtracting from 180.
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\n" ); document.write( "If it is not a right triangle, you can use the law of Cosines to find angle C.\r
\n" ); document.write( "\n" ); document.write( "You should find the largest angle first, because there can only be one angle in a triangle that is obtuse. The reason for finding it first is the next step, the sine rule, can only give us acute angles ( less than 90 degrees), so we avoid a possible wrong answer by first eliminating the only possibility of an obtuse angle.\r
\n" ); document.write( "\n" ); document.write( "c^2 = b^2 + a^2 = 2bacosC\r
\n" ); document.write( "\n" ); document.write( "cosC = a^2 + b^2 - 2abcosC\r
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\n" ); document.write( "\n" ); document.write( "cosC = a^2 + b^2 -c^2/2ab\r
\n" ); document.write( "\n" ); document.write( "From here, you can also obtain a second angle using the law of sines and third angle by adding the two and subtracting from 180.
\n" ); document.write( "Cleomenius. \n" ); document.write( "

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