**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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