Precal

Solve the given equation. (Enter your answers as a comma-separated list. Let k be any integer. Round terms to two decimal places where appropriate.)
cos θ = 0.16

I know how to find the answers when it's in fraction form, however, I do not know how to do it when the problem is in decimals. Is it correct to put the decimal into fractions or would that be wrong? Please help!

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  1. fractions are just numbers. Why is it any easier to find θ if

    cosθ = 4/25

    ?? You still have to evaluate cos^-1(x) using your calculator. Seems to me that using a decimal is even easier than using fractions.

    Now, if you have some problem like

    sin(arccos(.16)) then it would seem reasonable to use a fraction, since then it is clear that if

    cosθ = 4/25,
    sinθ = √84/25

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  2. I know how to find the answer with a fraction because those usually come out to become a 30-60-90 or 45-45-90 triangles. Or if they don't I use the pythagorean theorem to find the unknown side and figure out the problem that way.

    But I figured it out. The answer was 1.41+2pi(k),4.87+2pi(k).

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