A system is defined as an aggregation or assemblage of objects which interact to accomplish a set of goals or objectives. The smallest indivisible component of the system is called an entity. The variables associated with the entity which determine its state are called attributes. An instantaneous occurrence that changes the state of the system is called an event. For example, a frigate fitted with air defense weapons and sensors constitutes a naval air defense system; the missile fitted on the frigate is an entity; its probability of kill, range and velocity, are the attributes; detection, acquisition, firing and kill, are the events. N. K. Jaiswal, Military Operations Research : Quantitative Decision Making © Kluwer Academic Publishers 1997 the tank when fired from the direction <1>., we generate the projection of each of the J armor plates on a plane perpendicular to the line of fire. For this, we rotate the coordinate axes by an angle <1>. about Z-axis using the transformation J x = x cos . + y sin . new J J y = -x sin . + Ycos . new J J