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Can someone solve these questions please? I'm not getting the solution.

Can someone solve these questions please? I'm not getting the solution. 

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Grade:11

1 Answers

Aditya Gupta
2081 Points
5 years ago
cos22.5 can be found out using the formula
(cos2x+1)/2= cos^2x just put x=22.5 and note that cos45= 1/√2.
Also tan7.5 can be found out using tan2x= 2tanx/(1-tan^2x). We know that tan30=1/√3. So find tan15. And then find tan7.5
In the middle question use
cos 2x= 2/(1+tan^2x) - 1 

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