tan 0 + cot 0 =sec 0 csc 0?
We use following definitions of tangent, cotangent, secant and cosecant fuctions:
Also, from trigonometric circle or table with trigonometric values we know that:
So, given equation can be written as:
Notice that there two of denominators are zeros, so expressions on left and right side are not defined .
This means that equation is not valid!