View Full Version : Verifying Trigonometric ldentities
trigsucks09
Feb 18, 2008, 02:08 PM
Please help! I've been stuck for hours!
I need to prove the following identities and I've tried everything and can't get them to work!
(the * will stand for theta)
.) sin*+cos*cot*=csc*
.. ) 1/(1+cos*) + 1/(1-cos*)=2csc2*
... ) 1/(sin*) - 1/(tan*)=1
... ) sin*/(sin*-cos*)= 1/(1-cot*)
Please help!
ISneezeFunny
Feb 18, 2008, 02:14 PM
I usually don't like doing homework on this site for people...
but I've had a pretty good day so far, so I'll help you out with the first one.
remember that cot = 1/tan = cos/sin
remember that csc = 1/sin
so
sin* + (cos*)(cos*/sin*) = 1/sin*
multiply the entire thing by sin*
sin^2* + cos^2* = sin*/sin*
sin^2 + cos^2 = 1
this is true.
revs007
Feb 19, 2008, 06:05 AM
these all are very simple
1. let take the left hand side
sin*+cos* cot*
sin* + cos* . Cos*/sin*
taking LCM
sin^* + cos^* / sin* as sin^*+cos^* = 1
1/sin*
cosec* proved
2. 1/(1+cos*) + 1/(1-cos*)=2csc^*
again take left hand side to prove
aftre take lcm it will be
(1-cos*) + (1+cos*)
------------------------
( 1-cos*) ( 1+cos*)
2
-------------
(1-cos^*)
2/sin^*
2cosec^* proved
3. 1/(sin*) - 1/(tan*)=1
seems incomplete question
4. sin*/(sin*-cos*)= 1/(1-cot*)
take rhs this time
1/(1-cot*)
1
--- as cot* = cos*/sin*
1- cos*/sin*
taking LCm & cross mltipcation
sin*/sin* -cos* proved