Answer:
30
Step-by-step explanation:
→ You will pay $ 89.7.
The tip value is based on the bill value. Hence, to find the total payment you have to <u>multiply 78 by 1.15</u> (this includes the tip, 1.15).

Or you can <u>first find how many</u> 15% is from $78:

And then add this to $78:

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brainly.com/question/12901165
Π=180º
Cos(19π/6)=cos(19*180º/6)=cos (570º)=cos(210º+360º)=cos(210º)=
=-cos 30º=-√3 / 2≈-0.866...
Answer: cos(19π/6)=-cos 30º=-√3/2