Page 42 - DMTH201_Basic Mathematics-1

Unit 2: Trigonometric Functions-II

Notes
Let sin x = x = sin =
–1

or cos x =
–1

–1
–1
–1
+ cos x = or sin x + cos x =
–1
(ii) Let cot x = x = cot =

tan x = or + tan x =
–1
–1

–1
–1
or cot x + tan x =
(iii) Let cosec x =
–1
…x = cosec =

–1
–1
sec x = or + sec x =

–1
–1
cosec x + sec x =
Property 5

–1
(i) tan x + tan y =
–1

–1
–1
(ii) tan x – tan y =
Solution
(i) Let tan x = , tan y = x = tan , y = tan
–1
–1
–1
–1
We have to prove that tan x + tan y =
By substituting that above values on L.H.S. and R.H.S., we have

L.H.S. = + and R.H.S. =

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