V13 2 Let csc A with A in Q1 and find cos2A Preview TIP En

V13 2 ) Let csc A- with A in Q1 and find cos(2A) = Preview TIP Enter your answer as a number (like 5, -3, 2.2172) or as a calculation (like 5/3, 243, 5+4) Enter DNE for Does Not Exist, oo for Infinity

Solution

We have given cscA=sqrt(13)/2 with A in Q1

using sinA=1/cscA =1/(sqrt(13)/2)=2/sqrt(13)

sinA=2/sqrt(13),sin²A=4/13

cos2A=1-2sin²A=1-2(2/sqrt(13))^2=1-2*(4/13)=(13-8)/13=5/13

cos2A=5/13