Question

If a and b are complementary ,sin a is 4/5 find Cos b​

Answer 1

Answer:

$cos b=\frac{4}{5}$

Step-by-step explanation:

It is given that: a and b are complementary.

$\therefore a + b = 90\degree\\\\\therefore a = 90\degree - b\\\\Assuming\: sin \: ratio \: on\: both\: sides\\\\sin\:a = sin(90\degree - b)\\\\\therefore \frac{4}{5} = sin(90\degree - b)...(\because sin\:a = \frac{4}{5})\\\therefore \frac{4}{5} =cos\:b...\{\because sin(90\degree - \theta) = cos\: \theta\} \\\\\huge\purple{\boxed{\therefore cos\:b = \frac{4}{5}}}$