Question

please solve this with full explanation. no spam answer.​

Answer 1

Step-by-step explanation:

The given expression can be rearranged as:

(Cos 1 + cos 179) + (cos2 + cos 178) + (cos3+ cos177) +…. + (cos89 + cos 91) + (cos90) + cos180

But we know that: cos(180 - x)= - cos x, where x is angle in degree. So all the bracket totals except last 2 terms will be zero.

So given expression is: 0 + (cos90) + ( cos180)

= 0 + 0 + (-1)

=-1.

Answer: -1.

Answer 2

Answer:

b) 0

Step-by-step explanation:

cos 90°=0

0×(anything)=0

Hence answer is 0 .