Verify if sin25+sin35=cos5

Supposing that 25,35 and 5 are degrees, we'll transform
the sum of matching trigonometric functions into a
product.

We'll use the
formula:

sin a + sin b = 2sin
[(a+b)/2]*cos[(a-b)/2]

According to this formula, we'll
obtain:

sin 25 + sin 35 = 2sin
[(25+35)/2]*cos[(25-35)/2]

sin 25 + sin 35 = 2sin
[(60)/2]*cos[(-10)/2]

sin 25 + sin 35 = 2sin
30*cos(-5)

Since the cosine function is even, we'll
get:

sin 25 + sin 35 = 2sin
30*cos(5)

But sin 30 =
1/2

sin 25 + sin 35 =
(2/2)*cos(5)

sin 25 + sin 35 = cos
5