13-UJ 17 



14. Trigonometric ratios. If from any point /' in the ter- 



niiu -a distance r from the vertex, a 



perj , drawn to the initial .side meeting it m 



. 



, * 







I 



jtf, in I- 1 -e represented by y and VM by r, then, by 



general agreenx + if MP makes a positive r 



angle with the initial Inn-, and - if this ri-lit angle is 

 negative; Minil.i . s -f if VM extend* in tin- JM,^ 



i of the initial lints and if it -extends in the 



>n. 



< numlKTs r, r, and y form with each other six 

 s; these rati>>, IUMIVMVT, d-j>enil fur tli- ir value s<> 

 . the size of the angle 0, and not at all upon 

 r. These six ratios are known as the trigonometric ratios or 

 functions of the angle 0, and are named as follows : 



sine = ? f tangent = -, secant 6 = r , 



cosine 0s-, cotangent = -, cosecant = - 



The ited symbols for these functions are sin 0, 



coal, tau 6, cot 6, sec 0, and cscl, respt m< - 



H are not all independent, but are connected fl- 

 lo\vinjr relations : 



(1 ) =1, ^ cos 0: sin 0, 



) cos sec 6 = 1, (6) sin 1 6 + cos* = 1, 

 f j 1. -0+ 1 =sec*0, 



(4) tan = sin : cos 0, (8) cot0 + 1 uac j A 



>KOM. i 



