SOLUTION: Please help me to solve this assignment,Given that CosA=2/5,find the exact value of Cos2A
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Question 1190008: Please help me to solve this assignment,Given that CosA=2/5,find the exact value of Cos2A
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Look up "Double angles" on Wikipedia.
Answer by ikleyn(52835) (Show Source): You can put this solution on YOUR website!
.
Use the basic Trigonometry formula cos(2A) = 2*cos^2(A) - 1.
Substitute cos(A) = 2/5 here (as it is given), and complete the calculation on your own.
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See the compendium of basic Trigonometry formulas in the lesson
- FORMULAS FOR TRIGONOMETRIC FUNCTIONS
in this site.
In the future, consult this lesson every time as you need some basic Trigonometry formula.
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