Answer:
x=30o+n90on∈Z
Step-by-step explanation:
cos2x=sin(90o−2x)=sin(2x−30o)
Which mean 90o−2x=2x−30o+n360o
or 90o−2x+2x−30o=(2n+1)180o
The later cannot be true.
so x=30o+n90on∈Z
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
Answer:
D
Step-by-step explanation:
10/7 = 1.4285
9/y = 1.4285
Multiply both sides by y.
9 = 1.4285y
Divide both sides by y.
6.3 = y
Answer:
4 1/3
Step-by-step explanation:
12/3=4
1/3+4=4 1/3
