Question

Evaluate the following:

sin 10° – cos 80°

Answer 1

Given: sin 10° – cos 80°

Step-wise calculation:

1. Use the co-function identity cos θ = sin (90° – θ). 

So, cos 80° = sin (90° – 80°) 

= sin 10°

2. Substitute:

sin 10° – cos 80°

= sin 10° – sin 10°

= 0