Question 1104528
*[illustration rf1t.png].
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{{{4^2+Y^2=7^2}}}
{{{Y^2=49-16}}}
{{{Y^2=33}}}
{{{Y=sqrt(33)}}}
So,
{{{cot(cos^(-1)(4/7))=4/sqrt(33)=(4/33)sqrt(33)}}}