Problem 5
Start with the 30-60-90 triangle template
If you divide all values in that template by 2, then you'll get the diagram shown below.
Notice that the ratio of adjacent over hypotenuse leads to sqrt(3)/2
So that diagram shows that cos(30) = sqrt(3)/2
Answer: Choice A) 30 degrees
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Problem 6
Theta = 210 is between 180 and 270, which places the angle in quadrant Q3. This is in the southwest corner. In Q3, we have sine and cosine negative. They divide to make tangent positive
tan = sin/cos = negative/negative = positive
So tangent is positive in Q3
Answer: Choice C) tangent
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Problem 7
Cosine is an even function which means cos(-x) = cos(x) for all real numbers x.
So,
cos(170) = cos(-170)
Then we'll find a coterminal angle of -170 which involves adding on 360
-170+360 = 190
The angles -170 and 190 point in the exact same direction
This then means cos(170) = cos(-170) = cos(190)
Or in short, cos(170) = cos(190)
Answer: Choice A) cos(190)