Step-by-step explanation:
A left Riemann sum approximates a definite integral as:

Given ∫₂⁸ cos(x²) dx:
a = 2, b = 8, and f(x) = cos(x²)
Therefore, Δx = 6/n and x = 2 + (6/n) (k − 1).
Plugging into the sum:
∑₁ⁿ cos((2 + (6/n) (k − 1))²) (6/n)
Therefore, the answer is C. Notice that answer D would be a right Riemann sum rather than a left (uses k instead of k−1).
Answer:
$73.60
Step-by-step explanation:
Original price: $64
Markup: 0.15($64) = $9.60
New retail price: $64 + $9.60 = $73.60
4x-10 and 7x-8 are supplementary angles and thus add up to 180 degrees.
Thus, 11x - 18 = 180 degrees.
Combining like terms, 11x = 198, and x = 18.
The two supplementary angles are 4(18)-10 and 7(18)-8, or 62 and 118 degrees.
It's just a black screen for me
Is there a typo? I got none of those answers