document.write( "Question 1077637: Hi can someone help me with this problem please? THANK YOU \r
\n" ); document.write( "\n" ); document.write( " State the exact value of t,given cot t=-root3 and t [0,2pi) terminates QII \r
\n" ); document.write( "\n" ); document.write( " Select one
\n" ); document.write( " a.5pi/6
\n" ); document.write( " B.7pi/6
\n" ); document.write( " C. pi/3
\n" ); document.write( " D. 2pi/3
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Algebra.Com's Answer #692107 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
You do not need to memorize anything to figure out
\n" ); document.write( "the trigonometric ratios of a \"30-60-90\" right triangle
\n" ); document.write( "(one with acute angles measuring \"pi%2F6=30%5Eo\" and \"pi%2F3=60%5Eo\" ).
\n" ); document.write( "That triangle is half of an equilateral triangle.
\n" ); document.write( "If the length of the hypotenuse is \"1\" ,
\n" ); document.write( "the short leg's length is \"1%2F2\" ,
\n" ); document.write( "
\n" ); document.write( "and the Pythagorean theorem lets you figure out
\n" ); document.write( "the length of the other leg as \"h=sqrt%283%29%2F2\" .
\n" ); document.write( "So, for the \"pi%2F6=30%5Eo\" , we have the trigonometric ratios
\n" ); document.write( "\"sin%28pi%2F6%29=1%2F2\" , \"cos%28pi%2F6%29=sqrt%283%29%2F2\" , and \"tan%28pi%2F6%29=%281%2F2%29%2F%28sqrt%283%29%2F2%29=1%2Fsqrt%283%29\" .
\n" ); document.write( "Although cotangent is not as popular as sine, cosine, and tangent,
\n" ); document.write( "it is defined as \"cot%28theta%29=1%2Ftan%28theta%29\",
\n" ); document.write( "so \"cot%28pi%2F6%29=sqrt%283%29\" .
\n" ); document.write( "You know how angles in other quadrants relate to
\n" ); document.write( "symmetrical acute reference angles in quadrant I.
\n" ); document.write( "
\n" ); document.write( "In Quadrant II (QII for short), we have \"pi-pi%2F6=5pi%2F6=5pi%2F6\"
\n" ); document.write( "as the symmetrical angle to reference angle \"pi%2F6=5pi%2F6\" .
\n" ); document.write( "The absolute values of the trigonometric functions for those two angles are the same,
\n" ); document.write( "but some signs change:
\n" ); document.write( "\"sin%285pi%2F6%29=sin%28pi%2F6%29=1%2F2\" , \"cos%285pi%2F6%29=-cos%28pi%2F6%29=-sqrt%283%29%2F2\" ,
\n" ); document.write( "\"tan%285pi%2F6%29=-tan%28pi%2F6%29=-1%2Fsqrt%283%29\" , and \"cot%285pi%2F6%29=-cot%28pi%2F6%29=-sqrt%283%29\"
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\n" ); document.write( "NOTE:
\n" ); document.write( "To be able to say that you know trigonometry,
\n" ); document.write( "you should be able to figure out (not memorize without understanding)
\n" ); document.write( "the trigonometric functions for certain key angles.
\n" ); document.write( "You should start with \"0=0%5Eo\" and \"pi%2F2=90%5Eo\" ,
\n" ); document.write( "based on the unit circle definitions,
\n" ); document.write( "because you cannot use right triangle trigonometric ratios for those angles.
\n" ); document.write( "From there, you should also know the trigonometric functions' values
\n" ); document.write( "for all angles that are multiples of \"pi%2F2=90%5Eo\" .
\n" ); document.write( "Beyond that, there are key angles between \"0=0%5Eo\" and \"pi%2F2=90%5Eo\"
\n" ); document.write( "whose trigonometric ratios you should be able to figure out.
\n" ); document.write( "Consider a square of side length \"1\" , split in half by a diagonal.
\n" ); document.write( "The two halves are isosceles right triangles,
\n" ); document.write( "so both acute angles measure \"90%5Eo%2F2=45%5Eo=pi%2F4\" ,
\n" ); document.write( "and the length, x, of the legs of that right triangle,
\n" ); document.write( "can be figured out using the Pythagorean theorem.
\n" ); document.write( "Since \"2x%5E2=x%5E2%2Bx%5E2=1%5E2=1\" , \"x%5E2=1%2F2\" ,
\n" ); document.write( "and \"x=sqrt%281%2F2%29=1%2Fsqrt%282%29=sqrt%282%29%2F2\" .
\n" ); document.write( "No memorization needed.
\n" ); document.write( "For the \"30%5Eo=pi%2F6\" and \"60%5Eo=pi%2F3\" ,
\n" ); document.write( "consider an equilateral triangle with side length \"1\" (as shown above)
\n" ); document.write( "split into two congruent right triangles by one of its altitudes. .
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