Constructing Triangles from Angles. This Secret Agent Mission can be used to practice finding the missing angle in triangles. Students must know that the sum of the angles in a triangle is 180˚. Optional - Students will practice classifying triangles by their sides (scalene triangle, equilateral triangle, isosceles triangle) and angles (acute triangle, right triangle, obtuse triangle). Printable & Digital (EDITABLE).You want to be a Secret Agent, but first, you need to complete a training mi