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Trigonometry Trigonometric Question sin^2(180-x) cosec(270+x) + cos^2(360-x) sec(180-x)

Yazan975

Member
Sep 14, 2018
30
Screen Shot 2019-05-17 at 7.24.45 PM.png

In this question, I tried this:

sin^2(180-x) cosec(270+x) + cos^2(360-x) sec(180-x), where cosec(x) = 1/sin(x) and sec(x) = 1/cos(x)

-sin^2(180-x) = sin^2(x) and cos^2(x) = cos^2(x)

-The sin^2 and the 1/sin(x) cancle out along with the cos^2 and the 1/cos(x)

Therefore, I am left with sin(x)(270+x) + cos(x)(180-x)

This looks wrong. The answer on the answer sheet is -sec(x). I ask you for help please.
 

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
613
North Texas
$\csc(270+x) = \dfrac{1}{\sin(270+x)} = \dfrac{1}{\sin(270)\cos{x}+\cos(270)\sin{x}} = \dfrac{1}{-\cos{x}}$

$\sec(180-x) = \dfrac{1}{\cos(180-x)} = \dfrac{1}{\cos(180)\cos{x} + \sin(180)\sin{x}} = \dfrac{1}{-\cos{x}}$

...

$\dfrac{\sin^2{x}}{-\cos{x}} + \dfrac{\cos^2{x}}{-\cos{x}}$

can you finish from here?