What is a double angle identity to find the exact value of cos? Group of answer choices

cos⁡(2a)=〖cos〗^2⁡(a)+〖sin〗^2⁡(a)

cos⁡(2a)=〖cos〗^2⁡(a)

cos⁡(2a)=2 〖cos〗^2⁡(a)-1

cos⁡(2a)=〖2cos〗^2⁡(a)-2 〖sin〗^2⁡(a)

The line plot below represents the number of letters written to overseas pen pals by the students at the waverly middle school.each x represents 10 students. how many students wrote more than 6 and fewer than 20 letters. a.250 b.240 c.230 d.220