Question

find the value of cos (-9pi/4)

Answer 1

value of cos(-9pi/4) is 1/√2
edit:
first of all keep this in mind
cos(-x) = cos(x) (property of cosine)
secondly there's a simple procedure by graph you know cos(2pi)=0
9pi/4 = 2pi+pi/4 since the period of cos is 2pi (the curve repeats itself after every 2pi times) neglect that term and find cos(pi/4) -which i think we all know.

Answer 2

Answer:

$1 \div \sqrt{2}$

Step-by-step explanation:

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