Stain Measurement & Calculating Angles of Impact (Screencast)

In this learning object the student will learn how to measure a stain and calculate angles of impact. Determining the angle of impact for bloodstains takes advantage of the trigonometric functions (Sine function).

A mathematical relationship exists between the width and length of an elliptical bloodstain which allows for the calculation of the angle of the impact for the original spherical drop of blood.

Given well formed stains we can accurately measure the width and length by simply dividing the stain along it’s major and minor axis. The opposite halves would be generally equal to each other which aids in establishing the impact angle.

This screencast, we see how the shape of a stain defines the angle of impact. In general terms the more circular the stain, the more perpendicular will be the angle at which it struck the surface. The more elliptical the shape of the stain, the more acute the angle will be. With practice and experience, the analyst can recognize the general angle of impact based solely on the shape of the stain.

In this learning activity you'll apply the Law of Sines in the solution on an oblique triangle when provided with two angles and the side opposite one of the angles.

The target audience of this learning object is trigonometry students who have already learned what a radian is and have already derived the key values of the coordinates associated with common radian units, but now need to practice finding those values on the unit circle. The student does not need to know the definition of the six trig functions to do this activity.

Learners examine the use of the tolerances displayed in a title block by calculating the minimum and maximum allowable size of a fabricated part. In a brief quiz, students determine whether a part is usable or should be scrapped.