| Exam Board | Edexcel |
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| Module | PMT Mocks (PMT Mocks) |
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| Topic | Differentiation from First Principles |
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9. Given that \(x\) is measured in radians, prove, from the first principles, that
$$\frac { \mathrm { d } } { \mathrm {~d} x } ( \sin x ) = \cos x$$
You may assume the formula for \(\sin ( A \pm B )\) and that as \(h \rightarrow 0 , \frac { \sin h } { h } \rightarrow 1\) and \(\frac { \cos h - 1 } { h } \rightarrow 0\).