Looks like you just evaluated the summand for the given value of

, whereas the question is asking you to find the value of the sum for the first

terms.
Let

. Then

is the

th partial sum.

happens to be the first term in the series, which is why that box is marked correct:

But the next partial sum is not correct:

and this is not the same notion as the second term (which indeed is 0.75) in the series.
The answer is 8/9 i believe.
Answer:
sin 2x + cos x = 2 sin x cos x + cos x = (2 sin x + 1)cos x
Step-by-step explanation:
Given the expression: sin 2x + cos x,
then we can use the formula: sin 2x = 2 sin x cos x, which gives:
sin 2x + cos x = 2 sin x cos x + cos x = (2 sin x + 1)cos x
So there you have two expressions in terms of sin x and cos x, as requested. :D
6/962...............................................
I have no idea what this is asking honestly but i hope you figure it out