How do you find the exact values of cot, csc and sec for 90 degrees? Trigonometry Right Triangles Trigonometric Functions of Any Angle 1 Answer Somebody N. Apr 13, 2018 #color(blue)(csc(90^@)=1)# Explanation: Identities: #color(red)bb(cotx=1/tanx)# #color(red)bb(cscx=1/sinx)# #color(red)bb(secx=1/cosx)# We know: #sin(90^@)=1# #cos(90^@)=0# #tan(90^@)# is undefined. This is because: as #theta->90^@, tan(theta)->oo# #:.# #csc(90^@)=1/1=color(blue)(1)# #sec(90^@)=1/0# This is also undefined. ( division by zero ) #cot(90^@)# This is also undefind, because #tan(90^@)# is undefined. Answer link Related questions How do you find the trigonometric functions of any angle? What is the reference angle? How do you use the ordered pairs on a unit circle to evaluate a trigonometric function of any angle? What is the reference angle for #140^\circ#? How do you find the value of #cot 300^@#? What is the value of #sin -45^@#? How do you find the trigonometric functions of values that are greater than #360^@#? How do you use the reference angles to find #sin210cos330-tan 135#? How do you know if #sin 30 = sin 150#? How do you show that #(costheta)(sectheta) = 1# if #theta=pi/4#? See all questions in Trigonometric Functions of Any Angle Impact of this question 14468 views around the world You can reuse this answer Creative Commons License