We know $$sec^2 \alpha - tan^2 \alpha = 1$$
$$(sec \alpha + tan \alpha) (sec \alpha - tan \alpha) = 1$$
$$(sec \alpha - tan \alpha) = \frac{1}{2}$$
$$(sec \alpha + tan \alpha) = 2$$
$$sec \alpha = \frac{5}{4}$$
$$cos \alpha = \frac{4}{5}$$
$$sin \alpha = \frac{3}{5} = 0.6$$
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