It must be a right triangle to to use the trig. ratios.
A few easy ways to remember:
Some Old Horse Caught Another Horse Taking Oats Away.
or, SOCAHTOA.
Sine=SinA=opposite side of the ange over the hypotenuse of the triangle. a/h(hypotenuse)
Cosine=Cos=adjacent side of the angle over the hypotenuse of the triangle.
Tangent=TanAopposite side of the angleover the adjacent side of the angle.
Inverses:
Cosecant: Cosine Theta=1 over Sin Theta. Flip the sin to get and get the answer.
Secant: Secant Theta=1 over Cosine Theta. Flip the Cos and get the ansewr.
Cotangent: Cotangent Theta=1 over Tangent Theta. Flip the Tan to get the answer.