Question

The 3rd degree Taylor polynomial for cos(x) centered at a = π 2 is given by, cos(x) = − (x − π/2) + 1/6 (x − π/2)3 + R3(x). Using this, estimate cos(86°) correct to five decimal places.

Answer 1

Answer:

The cosine of 86º is approximately 0.06976.

Step-by-step explanation:

The third degree Taylor polynomial for the cosine function centered at $a = \frac{\pi}{2}$ is:

$\cos x \approx -\left(x-\frac{\pi}{2} \right)+\frac{1}{6}\cdot \left(x-\frac{\pi}{2} \right)^{3}$

The value of 86º in radians is:

$86^{\circ} = \frac{86^{\circ}}{180^{\circ}}\times \pi$

$86^{\circ} = \frac{43}{90}\pi\,rad$

Then, the cosine of 86º is:

$\cos 86^{\circ} \approx -\left(\frac{43}{90}\pi-\frac{\pi}{2}\right)+\frac{1}{6}\cdot \left(\frac{43}{90}\pi-\frac{\pi}{2}\right)^{3}$

$\cos 86^{\circ} \approx 0.06976$

The cosine of 86º is approximately 0.06976.