Head First 2D Geometry

evaluating new evidence

We’ve got a new sketch—now for a new

ballistics report

Following up on Benny’s story, officers have returned to the scene, and

found footprints, a broken window, and a set of tire trackes that might

indicate that he’s telling the truth. But there’s a big problem—from where

Charlie appeared to be standing, he can’t have shot Micky through the

door, plus the bullet that killed him came from the outside the building!

We do know that the bullet must have traveled in a straight line headed in

the direction shown on the sketch, but how it got there is the big question.

BULLET

PATH

DOOR

MICKY

BENNY

FOOTPRINTS

BROKEN

GLASS

18º

CRIME SCENE SKETCH

CASE GEO180

(ANGLES AS MEASURED

BUT DRAWING NOT TO

SCALE)

72º

CHARLIE

FOOTPRINTS

28º

158º

TIRE

TRACKS

56º

Q:

The dotted line extending the bullet path—how do we

know it’s really straight?

A:We’re going to start by saying that this line MUST be

straight heading backward from where the bullet entered the wall,

and then work up the sketch to find out how the bullet came to be

traveling in exactly that trajectory.

26 Chapter 1