Chapter 11 - Infinite Sequences and Series - 11.10 Taylor and Maclaurin Series - 11.10 Exercises - Page 811: 49

$cos 5^{ \circ}\approx 0.99619$ and calculator gives $0.996194696$

$cosx=Sigma_{n=0}^{\infty}(-1)^{n}\frac{x^{2n}}{(2n)!}$ $5^{ \circ}\times \frac{\pi}{180}=0.087266463$ $1-\frac{0.087266463^{2}}{2!}\approx 0.99619$ Hence, $cos 5^{ \circ}\approx 0.99619$ and calculator gives $0.996194696$