document.write( "Question 1118695: Solve the following equations for 0 ≤ θ ≤ 180 degrees.
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document.write( "6.a. sin^2 θ = 1
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document.write( "b. 3sin θ = 2cos θ
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document.write( "c. sin θ - 4cos θ = 0 \n" );
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Algebra.Com's Answer #734096 by Theo(13342)![]() ![]() You can put this solution on YOUR website! you can solve these graphically.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the graph of 6a is shown below:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " ![]() \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the graph of 6b is shown below:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " ![]() \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the graph of 6c is shown below:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " ![]() \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "to make graphing easier, i used x instead of theta.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "basically i created separate equations from the expression on the left side of the equal sign and the expression on the right side of the equal sign.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the intersection of those 2 equations is the common solution to both.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "i only looked for a solution between 0 and 180 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "that's the unshaded region of the graphs.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "to solve algebraically, i did the following/\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "6a equation is sin^2(x) = 1.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "remember, i'm using x in place of theta. \n" ); document.write( "this makes it easier to type and also easier to graph.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "take the square root of both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "sin(x) = plus or minus sqrt(1) = plus or minus 1.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "my calculator tells me:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "arcsin(1) = 90 degrees. \n" ); document.write( "arcsin(-1) = -90 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "to convert to all positive angles between 0 and 360 degrees, i do the following:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "90 degrees = 90 degrees \n" ); document.write( "-90 degrees = 360 - 90 = 270 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "i therefore get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "arcsin(1) = 90 degrees. \n" ); document.write( "arcsin(-1) = 270 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the only solution between 0 and 180 degrees is arcsin1) = 90 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "therefore 90 degrees is my only solution.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "6b equation is 3sin(x) = 2cos(x).\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "i'm using x instead of theta for purposes already described above.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "divide both sides of this equaation by 3 and divide both sides of this equation by cos(x) to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "sin(x)/cos(x) = 2/3.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since sin(x)/cos(x) is equivalent to tan(x), the equation becomes:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tan(x) = 2/3.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "arctan(2/3) = 33.69006753 degrees which can be rounded to 33.69 degrees as shown in the graph for 6b.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "that would be in the first quadrant.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tangent is positive in the first and third quadrant.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "third quadrant is not between 0 and 180 degrees, therefore the only solution is:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x = 33.69 degrees, as shown in the graph for 6b.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "6c equation is sin(x) - 4cos(x) = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "again, i use x in place of theta.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "add 4cos(x) to both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "sin(x) = 4cos(x)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "divide both sides of the equation by cos(x) to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "sin(x) / cos(x) = 4\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "this is equivalent to tan(x) = 4\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "arctan(4) = 75.96375653 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "this can be rounded to 75.964 degrees as shown in the graph for 6c.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tan is positive in the first and third quadrants only.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "third quadrant is not between 0 and 180 degrees.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "therefore the only solution is 75.964 degrees. \n" ); document.write( " |