document.write( "Question 1154926: Thank you for the help:\r
\n" );
document.write( "\n" );
document.write( "You are in a plane flying at an altitude of 900 feet. You see a statue at an angle of depression at 57 degrees. You also see a building at an angle of depression at 68 degrees. How far is the statue from the building? \n" );
document.write( "
Algebra.Com's Answer #777427 by jim_thompson5910(35256) ![]() You can put this solution on YOUR website! \n" ); document.write( "Here's one way to draw the diagram. The diagram is not to scale. \n" ); document.write( " ![]() \n" ); document.write( "The points are defined as follows: \n" ); document.write( "A = base of the statue \n" ); document.write( "B = base of the building \n" ); document.write( "C = point on the ground directly under point D \n" ); document.write( "D = plane's location \n" ); document.write( "E = point to help label the angles of depression\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The lengths we'll work with are \n" ); document.write( "CD = 900 (height) \n" ); document.write( "AB = x (distance between statue and building) \n" ); document.write( "BC = y\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The given angles of depression are \n" ); document.write( "angle ADE = 57 degrees (the upper angle shown in red) \n" ); document.write( "angle BDE = 68 degrees (the upper angle shown in blue)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Because DE and AC are horizontal lines, they are parallel. So we know that the alternate interior angles are congruent. This makes, \n" ); document.write( "angle DAC = 57 degrees (the lower angle shown in red) \n" ); document.write( "angle DBC = 68 degrees (the lower angle shown in blue)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "In other words, \n" ); document.write( "angle ADE = angle DAC = 57 (red pair of angles) \n" ); document.write( "angle BDE = angle DBC = 68 (blue pair of angles) \n" ); document.write( "because they are alternate interior angle pairs.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "For now, focus your attention on right triangle BCD. \n" ); document.write( "Ignore points A and E. Ignore the 57 degree angle for now. \n" ); document.write( "When we focus solely on triangle BCD, the label \"angle DBC\" can be simplified to the label \"angle B\". So B = 68.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We'll use the tangent ratio to solve for y. \n" ); document.write( "Recall the tangent of an angle is the ratio of the opposite over adjacent.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tan(angle) = opposite/adjacent \n" ); document.write( "tan(B) = CD/BC .... again we're only focusing on triangle BCD \n" ); document.write( "tan(68) = 900/y \n" ); document.write( "y*tan(68) = 900 \n" ); document.write( "y = 900/tan(68) \n" ); document.write( "y = 363.623603251641 ... use a calculator here; value is approximate \n" ); document.write( "Make sure your calculator is in degree mode.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Now we can use this to find x. We'll use another tangent ratio. This time, focus on triangle ACD. Ignore point B and its associated angle. Ignore point E.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tan(angle) = opposite/adjacent \n" ); document.write( "tan(A) = CD/AC \n" ); document.write( "tan(A) = CD/(AB+BC) \n" ); document.write( "tan(57) = 900/(x+y) \n" ); document.write( "tan(57) = 900/(x+363.623603251641)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Do a bit of algebra to solve for x. It might help to replace \"tan(57)\" with a variable such as z. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "tan(57) = 900/(x+363.623603251641) \n" ); document.write( "z = 900/(x+363.623603251641) \n" ); document.write( "z(x+363.623603251641) = 900 \n" ); document.write( "zx+363.623603251641z = 900 \n" ); document.write( "zx = 900-363.623603251641z \n" ); document.write( "x = (900-363.623603251641z)/z \n" ); document.write( "x = (900-363.623603251641*tan(57))/(tan(57)) ... plug in z = tan(57) \n" ); document.write( "x = 220.843230626119 \n" ); document.write( "I used a calculator for the last step. This value is approximate as well.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "No rounding instructions were given, so I would ask what your teacher wants you to round to. For now I'll just round to the nearest whole number.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Answer: Approximately 221 feet\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Edit: the tutor @MathTherapy has a much more elegant solution, so I would go with that method instead. Though the diagram is still handy to have. \r \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |