How do you solve number 27 and 28

Mathematics

1 answer:

Elanso [62]3 years ago

8 0

27) if a = 1/a

multiply both sides by a

a * a = 1/a * a

a^ 2 = 1

Answer is D) 1

28)

6 x 75 = 450

7 x 80 = 560

8 x 85 = 680

9 x 90 = 810

Total all students in class = 6 + 7 + 8 + 9 = 30 students

Total score of whole class:

450 + 560 + 680 + 810 = 2500

Average = 2500 /30 = 83.3 = 83 1/3

Answer is C) 83 1/3

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If tan theta = 12/5 and cos theta < 0, what is sin theta ?

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1 + tan ² Ф=sec²Ф
1+(12/5)²=sec²Ф
169/25=sec² Ф
sec Ф=⁺₋√(169/25)=⁺₋13/5

sec Ф=1/cos Ф ⇒cosФ=1/sec Ф
cos Ф>0 ⇔ sec Ф>0 ⇔ sec Ф=+ 13/5

cos Ф=1/secФ
cos Ф=1 / 13/5=5/13

we can calculate the sin Ф, with this method.
sin²Ф + cos²Ф=1 ⇒ sin Ф=⁺₋√(1-cos² Ф)
sin Ф=⁺₋√[1-(5/13)²]=⁺₋12/13
like cos Ф>0 and tan Ф>0 ⇒ sin Ф>0 ⇒sin Ф=12/13

answer: d.12/13

other method
tan Ф=sin Ф / cos Ф
12/5=sin Ф / 5/13
sin Ф=(12/5)*(5/13)=12/13

answer: d.12/13

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