Question

without using the calculator find the exact value of each trigonometry function.
a) sec(-210)
b) cos(-810)
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Answer 1

a) We know that sec(-theta) = sec theta

Therefore, sec (-210)

= sec (210)

= sec (3×90'-60') [formula]

= - cos 60' [since, theta lies in 2nd quadrant].

= - 1/2 (ANS)

b) We know that cos(-theta) = cos theta

Therefore, Cos (-810)

= cos (810)

= cos (9×90'+0')[formula]

= -cos 0' [ since, theta lies on the 2nd quadrant]

-1 (ANS)

I DONT HAVE THE PEOPER DEGREE SIGN THAT IS WHY I USED (') THIS SIGN AS DEGREE