Question

Please any one can answer questions no. 18&19

Answer 1

Solution:

Q19)

If
$tan \: 2A = cot(A - 18°) \\ \\ since \: \\ tan \: x = cot \: (90° - x) \\ \\ so \\ \\ cot \: (90° - 2A) = cot \: (A - 18°) \\ \\ cancel \: cot \: both \: sides \\ \\ 90° - 2A = A - 18° \\ \\ - 3A = - 108° \\ \\ A = 36°$

Q20)

Definition:

1) Complementary event:

In Probability complementary events are those which complements each other,
for eg

Happening of an event p(A)

So, if it does not happen than Probability p(A') = 1-p(A)

So,complementary event are those
p(A) +p(A')= 1

2) Impossible Event:

Those events which are impossible,probability of occurring of impossible event p(A)= 0

3) Certain/Sure event:

Certain or sure event are those which are sure to be occur.
like: universal truth

Probability of occurring an sure event p(A) = 1