# Autograph Newsletter 16 – 3D Special

 Welcome Welcome to the sixteenth Autograph Newsletter! Each jam-packed edition looks at a specific topic in mathematics and how Autograph can help engage students and enable them to understand the key concepts better.
 Introduction An often underused aspect of Autograph is its 3D capabilities. This is a crime against mathematics, as Autograph’s 3D engine is unique in the world of dynamic geometry in the way it allows students to visualise key concepts, manipulate objects, make predictions and test them out. This spans the word of graphing, geometry and calculus, meaning that benefits can be enjoyed by students of all ages and abilities. In this newsletter we will look at some of the many uses of Autograph in 3D.
 Diagnostic Question Diagnostic questions are ideal to use at the start of the lesson to enable you to get a quick and accurate picture of your students’ levels of understanding. They are designed in such a way that common misconceptions that your students may hold should steer them to one of the incorrect answers, thus allowing you to learn where the problems lie from their responses. Typically I give my class 30 seconds thinking time and then ask them to hold up their fingers: 1 for A, 2 for B, etc.
 Free Online Autograph Activity Discovering the Conic Sections Where do the conic graphs come from? Let’s find out! These Autograph activities do not require the full version of Autograph to run them. You just need to install the free Autograph Player (you will be guided through how to do this), which means you can use these activities in the classroom or set them for your students to do at home.
Ideas for Development
The following ideas for developing the topic of three-dimensions require the full version of Autograph.
Activity 1 – Transformations in 3D
Did you know it’s possible to carry out rotations in 3D?
 • To rotate in 3D we need a line, not a point. Can you explain why? • The blue object has been rotated 90° clockwise about the line x=1 to give the green object. • If you wiggle one of the corners of the original object, can you predict which corner of the image will move? • Use the  Animation Controller to see what happens as you change the angle of rotation. • To try out another rotation,  add a point, right-click and choose a line parallel to one of the axes. • Make sure the line and the object are selected, right-click and choose rotation from the menu. • Experiment to your heart’s content with rotations in 3D! • Challenge: Can you figure out how to carry out reflections and enlargements in 3D?
Activity 2 – Pythagoras and Trigonometry in 3D
Can your students work out the length of the diagonal of this 2x2x2 cube?
 • Use  Drag to take a look around the cube. • How can we work out the length of the diagonal line? • Are there any right angled triangles that can help us? • Create a line segment to help students see the appropriate right-angled triangle by selecting the points at two corners, right-click and choose Line Segment from the menu. • To check students answers, click View > Status Bar and select the line you want to measure. • If you also want to challenge the students to work out the value of the angles, select two line segments, right-click and choose Angle Between Lines.
Activity 3 – Volume of Revolution
The way Autograph brings the concept of volume of revolution to life in 3D is quite something!
 • Challenge your students to picture the solid that will form if we rotate the shaded area 360° around the x-axis • When you are ready, select  Slow Plot, left-click on the shaded area, right-click and choose  Find Volume. • Hold down left-click and drag the cursor around the screen to see the solid emerge • Now you can challenge your students to work out the volume. • A good way to start is to select the point at x = 3 and drag it closer to the other point (see Handy Autograph Tip below). • Students should hopefully see that the solid begins to resemble a cylinder the closer it gets, and following on from this the entire volume itself can be thought of as the sum of lots of these thin cylinders.
Activity 4 – Vector Golf 3D