Evaluate:

We have to find the value of

…(1)

…(∵ )

By the property of complementary angles, we know that .

∴ sin (90 – 80) = cos 80 ⇒ sin 10 = cos 80 …(3)

Alsosin (90 – 59) = cos 59 ⇒ sin 31 = cos 59…(4)

Equation (2) can be written as

…(From (3) and (4))

= 1 + 1 = 2

∴ The value of