SOLUTION: Evaluate: tan^2 (-405°) - sec^2 (-405°) + cos 900° Thank you

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Question 967036: Evaluate: tan^2 (-405°) - sec^2 (-405°) + cos 900°
Thank you
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
tan%5E2+%28-405%29+-+sec%5E2+%28-405%29+%2B+cos+900° =?
tan%5E2+%28-405%29+=+tan%5E2+%28-45%29+°
tan%5E2+%28-45%29=+sin%5E2+%28-45%29%2Fcos%5E2+%28-45%29°
since sin%5E2+%28-45%29=1%2F2 and cos%5E2+%28-45%29=1%2F2 we have tan%5E2+%28-45%29+=%281%2F2%29%2F%281%2F2%29=1
sec%5E2+%28-405%29+=+1%2Fcos%5E2+%28-45%29
since cos%5E2+%28-45%29=1%2F2=> 1%2Fcos%5E2+%28-45%29=2
cos+%28900%29+=cos+%28180%29=-1
so,
then, your answer is:tan%5E2+%28-405%29+-+sec%5E2+%28-405%29+%2B+cos%28+900%29=-2