
Concept explainers
If cost=−817 and if the terminal point determined by t is in Quadrant III, find tan t cot t + csc t.

To find: The value for tantcott+csct.
Answer to Problem 5T
The value of tantcott+csct is −215.
Explanation of Solution
Given:
The given trigonometric function is,
cost=−817
Calculation:
Use Pythagoras identities of fundamental identities.
sin2t+cos2t=1
Substitute −817 in the above equation to find the sint.
sin2t+(−817)2=1sin2t=1−(−817)2sin2t=1−64289sin2t=289−64289
Simplify the above equation,
sin2t=225289sint=√225289sint=±1517
Since the sint is negative in quadrant III.
sint=−1517
Use reciprocal identities of fundamental identities.
tant=sintcost. (1)
And,
csct=1sint. (2)
And,
cott=1tant. (3)
Substitute −817 for cost and −1517 sint in equation (1).
tant=−15/17−8/17tant=1517×178tant=158
Substitute 158 for tant in equation (3).
cott=115/8cott=815
Substitute −1517 for sint in equation (2).
csct=−115/17csct=−1715
Substitute 158 for tant, 815 for cott and −1715 for csct to find the value of tantcott+csct
tantcott+csct=158×815+(−1715)=1−1715=15−1715=−215
Hence, the value of tantcott+csct is −215.
Chapter 5 Solutions
Precalculus: Mathematics for Calculus - 6th Edition
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