Bc sin60 32 so b c32 a3. Area of a parallelogram. Area Of A Triangle Using Sine Studying Math Gcse Math Math Graphic Organizers Use the cosine rule to find the length of x for triangle ABC. . To find D use the triangle angle sum theorem which states that the sum of the three interior angles of a triangle is always equal to 180. Area of an ellipse. A Calculate the size of the largest angle of the triangle. Area of a trapezoid. In geometry area of rectangle is the region covered by the rectangle in a two-dimensional plane. A spherical polygon is a polygon on the surface of the sphere defined by a number of great-circle arcs which are the intersection of the surface with planes through the centre of the sphereSuch polygons may have any number of sides. Sides of a Triangle. Cosine rule in trigonometry is used to find the sides and angles of a triangle. Learn to prove the rule with examples at BYJUS.