Geo5.4.5

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Find the area of the triangle formed by the points (-3,-30^{\circ }),(5,150^{\circ }),(7,120^{\circ })\,

Area of the triangle is

{\frac  {1}{2}}[(-3)(5)\sin(-30-150)+(5)(7)\sin(150-120)+(7)(-3)\sin(120+30)]\,

{\frac  {1}{2}}[15\sin 180+35\sin 30-21\sin 150]\,

{\frac  {1}{2}}[0+{\frac  {35}{2}}-{\frac  {21}{2}}]\,

{\frac  {1}{2}}[7]={\frac  {7}{2}}\,


Main Page:Geometry:Polar Coordinates