Fallacies about the Derivative of the Trigonometric Sine Function

TOH Tin Lam, TAY Eng Guan, and TONG Cherng Luen

National Institute of Education
Nanyang Technological University
Singapore

Published in The Mathematician Educator, 2021, Vol 2, No. 1, pp 1-10.

Abstract

In this paper, several fallacies about the extension of the formula $\frac{d}{dx} (\sin x) = \cos x$ to the erroneous formula $\frac{d}{dx} (\sin x^\circ) = \cos x^\circ$ are discussed. In a Commognitive Theory Framework, misconceptions by ‘newcomers’ can be traced to the use of the word “unit”.

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