Question #cd107

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Answer 1 · 2015-01-31T23:55:52

Let's first draw a triangle to get the trigonometry right.

enter image source here
We'll use #angleA# instead of #x# because of the picture

#cosA# is defined as #b//h#
#tanA# is defined as #a//b#

So we get: #cosA*tanA=cancelb/h * a/cancelb=a/h#

Which is the definition of the sine .

Answer :
#cosA*tanA=sinA#

Extra
You could have done this another way if you knew that

#tanA=sinA/cosA#

Then it would be:

#cosA*tanA=cancel(cosA)*sinA/cancel(cosA)=sinA# (same result)

(picture: Wikipedia)

Answer 2 · 2017-11-07T15:40:09

# cosx tanx -= sinx #

# cosx tanx -= cosx * sinx/cosx -= sinx #