In the co-ordinate plane, consider a point A on the positive side of x-axis. Let this point revolve about the origin in the anti-clockwise direction through an angle θ and reach the point P.

OL = x = Adjacent side

PL = y = Opposite side

OP = √(x2 + y2)= Hypotenuse (= r > 0)

The six trigonometrical ratios or circular functions are defined as:

sin θ = y/r

cosec θ = r/y

cos θ = x/r

sec θ = r/x

tan θ = y/x

cot θ = x/y

cosec θ, sec θ and cot θ are the reciprocals of sin θ, cos θ and tan θ respectively.

Signs of T-Functions

T-Ratios of Particular Angles