Find the value of cos11π/12?
2 Answers
Jun 12, 2018
Explanation:
using the trigonometric identity
∙xcos(x+y)=cosxcosy−sinxsiny
note that 11π12=2π3+π4
cos(11π12)=cos(2π3+π4)
=cos(2π3)cos(π4)−sin(2π3)sin(π4)
=−cos(π3)cos(π4)−sin(π3)sin(π4)
=(−12×√22)−(√32×√22)
=−√24−√64=−14(√2+√6)
Jun 12, 2018
Explanation:
Find
In this case:
Finally,
Check by calculator.
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