# right angled triangle

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LIE 4ii I
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labReports.pdf
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120 mm
40 mm
Figure 2: A right angled triangle with sides measured to the nearest 0.25 millimneters
2.6.1) that a figure should be given to, it is necessary to determine firstly, the accuracy to which the value was recorded and secondly the situation it will be used. For example, if the angle of a slope, such as that shown in figure 2 is being determined the length and height of the right angled triangle and the length is measured with a standard ruler, the precision of length measurements will be to the nearest 0.5 mm. If the length of sides of the right angled triangle are 120 mm and 40 mm, then the trigonometry yields and angle of 19.47122063449069 degrees. However, given the accuracy of the ruler, the lengths could be of value 121 mm and 39 mm or 119 mm and 40 mm, giving angles of 18.80292666433218 degrees and 20.15358484435286 degrees. Therefore, giving that the accuracy of the slope measurement is only to the nearest 1 degree, giving the value to 16 significant figures is not only pointless, it is also confusing for the reader. If a value of 19.47122063449069 degrees is given in a lab report, it will be assumed by the reader that this angle has been measured to this level of precision, which it has not. In addition, if the angle of the slope has been measured to this level of precision, it may still not be appropriate to quote with 16 significant figures if the value is used in subsequent calculation. For example, if the value of angle is to be used in a calculate the force experienced as due to a body placed on the slope, the result of the calculation will be dependant on the accuracy and precision of the measurement of the body’s mass. Unless the mass measurement has been made to an equally high precision as the measurement of the slope angle, then the additional significant figures will be useless. Therefore, whenever numerical information is presented, care most be taken to ensure that units are provided if necessary and the number significant figures is appropriate.
4 Conclusions
The principle message to adopt from this document is that engineering laboratory reports are professional documents and as such should be written with a professional approach. It is important the report is well written, detailed, concise, logical and consistent. The points mentioned are summarized below to act as a check list for lab reports:
• Is a title page needed and if so has it got the title of the report, the date and author’s
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