Ten top tips for the GCD

The International Baccalaureate mathematics examinations require you to be familiar with a graphical display calculator. Here, I discuss the use of the GDC in Standard and Higher Level mathematics.

So you’ve just been handed a brand new graphical display calculator (GDC) for your IB maths course. There’s a good chance that you have been given a Texas Instruments Ti-84+ or a Casio FX-9860. If you did the MYP programme, then you may have used a GDC before. But if you took the GCSE or IGCSE, then it will be new to you.

I lay out some tips and thoughts below for using your GDC.

  1. Don’t expect your teacher to show you all the features of the GDC. If you don’t understand how to do a particular operation, there are great tutorials on Youtube. See the list of links at the end of the article. For more complex queries, you may need to download the manual if you don’t have a hard copy.

  2. Do take it to class every day. Although there will be times when you don’t need it, you don’t want to be borrowing one off your neighbour. Put your name on it so you don’t lose it.

  3. Remember that in paper 2 (SL or HL) and both papers (Studies) you are going to need your calculator to do many of the questions. Don’t try to do long-winded calculations by hand when there is a quick method using the GDC. You won’t get extra credit and you increase your chance of making mistakes. You need a different way of thinking when tackling calculator questions. All good IB textbooks identify whether a question is intended for the calculator or not.

  4. First and foremost, the graphing calculator can solve equations and inequalities graphically for you. But like drawing any graph, you need to tell the calculator the range of values for the x and y axes. This is called the WINDOW. If you don’t get the WINDOW right, you won’t see any curve on your display.

  5. All GDCs have a ZOOM function to zoom in and out of regions of interest on the graph you have plotted.

  6. For calculations involving angles (sine, cosine, etc), you need to know if you are working in degrees or radians. Make sure you know how to change the mode of the calculator. In IB, you are usually working in radians. The sine of ten degrees is not the same as the sine of ten radians.

  7. The statistical functions on the calculator are very powerful. Make sure that you learn how to enter data sets, display a scatter diagram and work out mean, median and other common statistical functions.

  8. Don’t confuse the ‘subtract’ and the ‘minus’ operations. These are distinct and not accessed by the same key. Minus for entering a negative number. Subtract for taking away.

  9. Beware of raising a negative number to a power. Put all negative numbers in brackets first if they are to be raised to a power. Try both ways – you will see what I mean.

  10. Practise makes perfect. Don’t leave learning the calculator skills to the last minute.

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