86 



PRACTICAL MATHEMATICS 



56. The Inverse Trigonometrical Functions. 

 (1) If y = sin" 1 x 



Then x = sin y 



and 



L 



-T- = cos y = V 1 x z (Fig. 27) 

 ay 



(2) If y = cos- 1 x 

 then 



and 



(Fig. 28) 



(3) If y = tan- 1 x 



then # = tan y 



dx 



and ^ = sec 2 y = 1 + x z (Fig. 29) 



a?/ 



dy 



