Question

Just the answer please.
1: http://imgur.com/XE1GEyV
2: http://imgur.com/4RJe93Q

Answer 1

Answer on Question #58896 – Math – Trigonometry

Question

Which of the following could not be points on the unit circle?

$$\left(- \frac {2}{3}, \frac {\sqrt {5}}{3}\right)$$ $$(0.8, - 0.6)$$ $$(1, 1)$$ $$\left(\frac {\sqrt {3}}{2}, \frac {1}{3}\right)$$

Solution

Pairs (1,1) and $\left(\frac{\sqrt{3}}{2},\frac{1}{3}\right)$ could not be points on the unit circle, because the distance between a point and the center is not equal to 1, that is,

$$\sqrt {1 + 1} = \sqrt {2} \neq 1,$$ $$\sqrt {\frac {3}{4} + \frac {1}{9}} = \sqrt {\frac {31}{36}} \neq 1.$$

Answer: (1,1), $\left(\frac{\sqrt{3}}{2}, \frac{1}{3}\right)$.

Question

If $P(x, y)$ is the point on the unit circle determined by real number $\theta$, then $\tan \theta = \_$.

$$\frac {1}{x}$$ $$\frac {1}{y}$$ $$\frac {y}{x}$$ $$\frac {x}{y}$$

Answer: $\tan \theta = \frac{y}{x}$.

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