Solve cos72^circcos18^circ-sin72^circsin18^circ=

$$\cos 72 ^ { \circ } \cos 18 ^ { \circ } - \sin 72 ^ { \circ } \sin 18 ^ { \circ } =$$

Evaluate

$$0.000000000000000047552825814757675$$

Solution Steps

Evaluate trigonometric functions in the problem

$$0.30901699437494745 \cdot 0.9510565162951535 - 0.9510565162951535 \cdot 0.3090169943749474$$

Multiply 0.30901699437494745 and 0.9510565162951535 to get 0.293892626146236566929330252183575.

$$0.293892626146236566929330252183575-0.9510565162951535\times 0.3090169943749474$$

Multiply 0.9510565162951535 and 0.3090169943749474 to get 0.2938926261462365193765044374259.

$$0.293892626146236566929330252183575-0.2938926261462365193765044374259$$

Subtract 0.2938926261462365193765044374259 from 0.293892626146236566929330252183575 to get 0.000000000000000047552825814757675.

$$0.000000000000000047552825814757675$$

Factor

$$\frac{7591 \cdot 12969037 \cdot 139 ^ {2}}{2 ^ {33} \cdot 5 ^ {31}} = 4.755282581475767 \times 10^{-17}$$