I need help proving this ASAP

1 + tan²A = sec²A = 1/cos²A

2tan(X/2)/(1+tan²(X/2))

= 2tan(X/2)cos²(X/2)

= 2[sin(X/2)÷cos(X/2)]cos²(X/2)

= 2sin(X/2)cos(X/2)

= sin(X)

Because sin(2A) = 2sin(A)cos(A)

the sum of the lengths of any two sides of a triangle is greater than the length of the third side. if you take the three sides of a triangle and add them in pairs, the sum is greater than (not equal to) the third side. if that is not true, then it is not possible to construct a triangle with the given side lengths.

step-by-step explanation:

wedfghjkl;

tyuiop[]ghjkl;

step-by-step explanatio89