if A+B=180(degrees) , then which of the following is true?
( 1 ) sinA=sinB
( 2 ) cosA=cosB
( 3 ) tanA=tanB

a. (1) only b. (2)only c. (3)only d. all of them

Question

if A+B=180(degrees) , then which of the following is true?
( 1 ) sinA=sinB
( 2 ) cosA=cosB
( 3 ) tanA=tanB

a. (1) only   b. (2)only   c.  (3)only   d. all of them

hartnn · Answer

sin(180-x)=sin x 
cos(180-x)=-cos x
tan(180-x)=-tan x
does this help ?

anonymous · Answer

how actually will i do that?

hartnn · Answer

A+B=180
A=180-B

anonymous · Answer

owh yeah.. i also did that but when i tried to use 90 degrees, it went undefined when finding its tan.. so (1) and (2) are the only correct answers but it don't have that kind of answer.. will i substitute other value for A and B?? but i taught i will find myself doing it so long just to prove the equality.. :((

hartnn · Answer

sin(180-B)=sinB<---true
cos(180-B)=cos B<---false
tan(180-B)=tanB<---false

anonymous · Answer

how is that?? i dont get it :((

anonymous · Answer

owh i get it now :)) thanks!

hartnn · Answer

these are identities:
sin(180-x)=sin x 
cos(180-x)=-cos x
tan(180-x)=-tan x

now put x=B there.
also A=180-B

hartnn · Answer

oh, u got. great :)

anonymous · Answer

ok ok.. i forgot about the odd-even identities :)) hehe..
thanks by the way... more powers to come!! :))

hartnn · Answer

welcome :)