Question

Sin a cos a ctg a -1​

Answer 1

$\sin a\cos a\cdot \mathrm{ctg}a-1=\sin a\cos a\cdot \frac{\cos a}{\sin a}-1=\cos^2a-1=-\sin^2 a$

Answer 2

It looks like you have an expression involving trigonometric functions. If you want to simplify it, here's what you can do step by step:

sin(a) * cos(a) * cot(a) - 1

First, let's express cot(a) in terms of sine and cosine:

cot(a) = cos(a) / sin(a)

Now, replace cot(a) with this expression:

sin(a) * cos(a) * (cos(a) / sin(a)) - 1

Next, simplify the expression by canceling out common factors:

sin(a) * (cos(a) * cos(a)) / sin(a) - 1

The sin(a) in the numerator and denominator cancels out:

cos(a) * cos(a) - 1

Finally, you have:

cos^2(a) - 1

If you're looking for a trigonometric identity to apply, this simplifies further using the Pythagorean identity:

cos^2(a) - sin^2(a) = 1

So, you can replace cos^2(a) with 1 + sin^2(a):

1 + sin^2(a) - 1

The "1" terms cancel out, and you're left with:

sin^2(a)

So, the simplified expression is sin^2(a).