### Question Description

use the definitions of trigonometric ratios for a right triangle to derive a cofunction identity for the expression.

cot(90°-A)

## Explanation & Answer

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cot(90-A) which in this case to keep it simple A=x

cot(90-x)

tanx

reference: http://www.mathwords.com/t/trig_identities.htm

Most of these types of things are rules and you must memorize I struggled with the same thing. You can also graph both of them to see that they overlap since cot is 1/tanx by have tan(90-x)=cotx and cot(90-x)=tanx