Remember that the sine of an angle in a right triangle is equal to the quotient between the side opposite to the angle and the hypotenuse of the triangle.
Since the sine of the given angle θ is equal to 3/5, we can represent θ as part of a right triangle whose hypotenuse has a measure of 5 and the side opposite to θ has a measure of 3:
The length of the side adjacent to θ must be equal to 4 in order to satisfy the Pythagorean Theorem:
[tex]3^2+4^2=5^2[/tex]On the other hand, the cosine of an angle is defined as the quotient between the side adjacent to the angle and the hypotenuse of the triangle. Then, the cosine of θ must be equal to 4/5:
[tex]\cos \theta=\frac{4}{5}[/tex]The rest of the trigonometric relations are defined in terms of the sine and the cosine as follows:
[tex]\begin{gathered} \tan \theta=\frac{\sin \theta}{\cos \theta} \\ \cot \theta=\frac{\cos \theta}{\sin \theta} \\ \sec \theta=\frac{1}{\cos \theta} \\ \csc \theta=\frac{1}{\sin \theta} \end{gathered}[/tex]Since sinθ=3/5 and cosθ=4/5, then:
[tex]\begin{gathered} \tan \theta=\frac{3}{4} \\ \cot \theta=\frac{4}{3} \\ \sec \theta=\frac{5}{4} \\ \csc \theta=\frac{5}{3} \end{gathered}[/tex]
