Question

Verify the identity. tan x + pi /2= -cot x

Answer 1

Surely it's

tan (x + pi /2) = -cot x ??

Answer 2

You can't just use the tan(a+b) identity because you would get some tan(pi/2) which is undefined.

But you CAN use the definition of tana=sina/cosa.

So you have:
\[\Large \tan \left( x+\dfrac{\pi}{2} \right)=\frac{ \Large \sin \left( x+\dfrac{\pi}{2} \right) }{ \Large \cos \left( x+\dfrac{\pi}{2} \right) }\]

Then just expand each of the num'r and den'r using the sum identities for sine and cosine, and I bet everything will fall into place. :)

Answer 3

can you help me

Answer 4

do you know the trig sum identities?

what's sin(a + b) = ?
what's cos(a + b) = ?

Answer 5

sina+b+sinacosb

Answer 6

?

Answer 7

http://www.mathplanet.com/images/math/codecogs_ca939b37.gif

Answer 8

ok

Answer 9

im lost

Answer 10

hmm? well, where at?

Answer 11

an you show me step by step

Answer 12

ok, do you see the sum identities in the picture?

what would be sin(a +b)?
what would be cos(a+b)?

Answer 13

yes

Answer 14

can you read this one => https://mathtestpreparation.com/Lessons/TrignSumADifForFig1.gif maybe

Answer 15

so, what would be sin(a +b)?
what would be cos(a+b)? as expanding the identity

Answer 16

confused? where? :)

Answer 17

how do you expand