$\sec(\theta)=x/5$.
What does $\sin(\theta)$ equal? What does $\tan(\theta)$ equal?
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9Draw out a representative right triangle with theta as one of the acute angles. What proportion of sides is the secant function? Can you find the value of all the sides? And from there, can you find sine and tangent? – Michael Chen Apr 28 '11 at 23:32
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3Look at "List of trigonometric identities, Trigonometric functions" in Wikipedia http://en.wikipedia.org/wiki/Trigonometric_identity – Américo Tavares Apr 28 '11 at 23:45
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Here is my answer to a similar, though not identical, problem. – Isaac Apr 29 '11 at 03:49
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As Michael Chen has alluded to:
Start by noting that
$$\sec \theta = \frac{1}{\cos \theta} = \frac{x}{5}$$
so that $$\cos \theta = \frac{5}{x}$$
Now you know that $\cos \theta$ is the 'adjacent / hypotenuse ' of a right angled triangle. So...draw the triangle, and work out what the unknown side ('opposite') will be, and then use the definition of $\tan$ and $\sin$.
Juan S
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@sara: To "work out... the unknown side", use the Pythagorean Theorem with x as the length of the hyponetuse. – The Chaz 2.0 Apr 29 '11 at 04:58