Question

The value of cos 10° + cos20° + ...cos80° is

please solve it and I'll mark it as brainliest....​

Answer 1

Step-by-step explanation:

Cos 10° + cos 20°........ Cos 80°

Since Cos 80° can be written as Sin 10°

Similarly all the other Cos theta degrees will get converted to Sin theta degrees after Cos 40°

Therefore

Cos 10° + Sin 10° = 1

So 40 will be the answer.