Lecture Notes Trigonometric Identities 1 page 2
Practice Problems
Prove each of the following identities.
cos x 1 cot x ! 1 1 ! tan x
1. tan x + = 11. =
1 + sin x cos x cot x + 1 1 + tan x
2. tan2 x + 1 = sec2 x 12. (sin x + cos x) (tan x + cot x) = sec x + csc x
1 1 sin3 x + cos3 x
3. ! = 2 tan x sec x 13. = 1 ! sin x cos x
1 ! sin x 1 + sin x sin x + cos x
4. tan x + cot x = sec x csc x cos x + 1 csc x
14. 3 =
sin x 1 ! cos x
1 + tan2 x 1
5. = 1 + sin x 1 ! sin x
2
1 ! tan x cos2 x ! sin2 x 15. ! = 4 tan x sec x
1 ! sin x 1 + sin x
6. tan2 x ! sin2 x = tan2 x sin2 x 16. csc4 x ! cot4 x = csc2 x + cot2 x
1 ! cos x sin x sin2 x 1 ! cos x
7. + = 2 csc x 17. =
sin x 1 ! cos x 2
cos x + 3 cos x + 2 2 + cos x
sec x ! 1 1 ! cos x tan x + tan y
8. = 18. = tan x tan y
sec x + 1 1 + cos x cot x + cot y
9. 1 + cot2 x = csc2 x
1 + tan x cos x + sin x
19. =
csc2 x ! 1 1 ! tan x cos x ! sin x
10. = cos2 x
csc2 x
20. (sin x ! tan x) (cos x ! cot x) = (sin x ! 1) (cos x ! 1)
c copyright Hidegkuti, Powell, 2009
" Last revised: May 8, 2013