Evaluate the following limits:
As we need to find
We can directly find the limiting value of a function by putting the value of the variable at which the limiting value is asked if it does not take any indeterminate form (0/0 or ∞/∞ or ∞-∞, .. etc.)
Let Z
∴ we need to take steps to remove this form so that we can get a finite value.
Tip: Similar limit problems involving trigonometric ratios are mostly solved using sandwich theorem.
So to solve this problem we need to have a sin term so that we can make use of sandwich theorem.
Note: While modifying be careful that you don’t introduce any zero terms in the denominator
As,
Multiplying numerator and denominator by 1-cos x, We have-
⇒ Z =
{As 1-cos2x = sin2x}
⇒ Z =
To apply sandwich theorem, we need to have limit such that variable tends to 0 and following forms should be there
Here x→ π so we need to do modifications before applying the theorem.
As, sin (π-x) = sin x or sin (x - π) = -sin x and tan(π – x) = -tan x
∴ we can say that-
sin2x = sin2(x-π) and tan2x = tan2(x-π)
As x → π
∴ (x – π) → 0
Let us represent x - π with y
∴ Z =
Dividing both numerator and denominator by y2
Z =
⇒ Z = {Using basic limits algebra}
As,
∴ Z =
∴