Solve -sin18^circ/cos72^circ

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

Evaluate

$$-\frac{6180339887498948}{6180339887498949}\approx -1$$

Solution Steps

Evaluate trigonometric functions in the problem

$$\frac{-0.3090169943749474}{0.30901699437494745}$$

Expand \frac{-0.3090169943749474}{0.30901699437494745} by multiplying both numerator and the denominator by 100000000000000000.

$$\frac{-30901699437494740}{30901699437494745}$$

Reduce the fraction \frac{-30901699437494740}{30901699437494745} to lowest terms by extracting and canceling out 5.

$$-\frac{6180339887498948}{6180339887498949}$$

Factor

$$-\frac{6180339887498948}{6180339887498949} = -0.9999999999999999$$