Question

the value sinA cos A is 1.why

Answer 1

Who said that the value of sinA .cosA is equal to 1
Let me prove this
A=0 (say)
sin 0=0
cos 0= 1
sin0.cos0=1
Let's take one more value of A
A=45 (say)
sin 45=1/√2
cos 45=1/√2
sin 45.cos 45=1/2
so sinA.cosA is never equal to 1

Answer 2

SinA CosA is not equal to one
Sin 2A=2Sin A Cos A
so SinA Cos A=1/2 Sin2A
we know 0≤sin A≤1
So 0≤Sin2A ≤1/2
Max value of sin a cos a is 1/2
and min value is 0
it can't be equal to 1
hope this helps