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so. hmm which is it? the +/- ? well, neverminding for a second, the value of tangent, just looking at the sign, the tangent is positive,
tangent = opposite/adjacent.... so that only happens, when both are the same sign, + or - both
now, we know the sine is -1/5.. if the sine is negative, the cosine also has t to be negative, so we'd use the -2√(6) = a
thus
Answer:
Diameter is basically double the radius, a physical representation of it is a full line that goes across the middle of the circle, if that makes sense. So you do 2 x 2 = 4 units
Hope that answers your question