Using the three trigonometric functions can be used to calculate unknown side lengths and angle in a right-angle triangle only.
But, if ever you we're given to find a non right-angle triangle, you will have to use sine rule or cosine rule.
Answer:
Step-by-step explanation:
n=12.4+23.79-5.27
n=30.92
The value would be -35.357.
So, we know the sum of the first 17 terms is -170, thus S₁₇ = -170, and we also know the first term is 2, well

well, since the 17th term is that much, let's check what "d" is then anyway,
It's called an obtuse angle.