What is the exact value of cos(11pi/21)cos(pi/7)-sin(11pi/21)s in(pi/7)? a. -squr3/2
b. -1/2
c. 1/2
d. squr3/2

i think it is everything has to equal 180 so, if i correct 4=c. 6=d. 8=a. 7=b. and the last question would be c. because they are parallel lines and they are congruent.

step-by-step explanation:

the reason everything has to equal to 180 is because that is how it works. i'm guessing that is its rule. 4 and 8 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 6 and 7 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 60+60 is 180. so, now you have your answer

it is contrapositive

i could not see the question too well so check yourself again too . this is because i want you to get it correct.

answer: i wpould go with c

step-by-step explanation: