gsdagasdf
@sourwing
@radar
Not familiar with this problem, it appears that "t" is Quadrant IV.
Draw a diagram.
draw a pic of what?
he reference angle for t.
so we know that angle "t" is between \(\bf \cfrac{3\pi}{2}<t<2\pi\) so as radar said, that puts it in the IV Quadrant so... we know that in the IV Quadrant, cosine is positive, and sine is negative
ok so what do we do with this info
so \(\bf sec(t)=\cfrac{13}{5}\iff \cfrac{1}{cos(t)}\implies \cfrac{1}{cos(t)}=\cfrac{13}{5}\\ \quad \\ 5=13cos(t)\implies \cfrac{5}{13}=cos(t)\\ \quad \\ \quad \\ cos(t)=\cfrac{5}{13} \implies \cfrac{adjacent}{hypotenuse} \implies \cfrac{a=5}{c=13} \\ \quad \\ \textit{using the pythagorean theorem }c^2=a^2+b^2\implies \sqrt{c^2-a^2}={\color{blue}{ b}}\\ \quad \\ \quad \\ \textit{keeping in mind that }sin(t)=\cfrac{{\color{blue}{ b}}}{c}\)
the pythagorean theorem root, doesn't tell us whether is negative or positive but we know is in the IV Quadrant, thus you'd use the negative value for "b" once you have "b", you'd have the sin(t) the cos(t) is given, and then just plug them in the given expression
thanks so much
yw
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