Math  /  Trigonometry

QuestionEach of the following are equal to Sin(A)\operatorname{Sin}(A) EXCEPT
A sin(A)\sin (-A) B sin(πA)\sin (\pi-A) (C) cos(90A)\cos \left(90^{\circ}-A\right)
D 1cscA\frac{1}{\csc A}
SUBMIT ANSWER

Studdy Solution

STEP 1

What is this asking? Which of these expressions is *not* equal to sin(A)\sin(A)? Watch out! Remember your trigonometric identities and the relationships between sine and cosine!
Also, be careful with signs and angles.

STEP 2

1. Analyze option A
2. Analyze option B
3. Analyze option C
4. Analyze option D

STEP 3

We're given sin(A)\sin(-A).
The sine function has a special property: it's an **odd function**!
This means sin(A)=sin(A)\sin(-A) = -\sin(A).
So, option A is *not* equal to sin(A)\sin(A).

STEP 4

We have sin(πA)\sin(\pi - A).
Remember the **sine subtraction formula**: sin(xy)=sin(x)cos(y)cos(x)sin(y)\sin(x - y) = \sin(x)\cos(y) - \cos(x)\sin(y).

STEP 5

Let's apply this to our expression: sin(πA)=sin(π)cos(A)cos(π)sin(A) \sin(\pi - A) = \sin(\pi)\cos(A) - \cos(\pi)\sin(A)

STEP 6

We know that sin(π)=0\sin(\pi) = \textbf{0} and cos(π)=-1\cos(\pi) = \textbf{-1}.
Substituting these values, we get: sin(πA)=(0)cos(A)(-1)sin(A)=sin(A) \sin(\pi - A) = (\textbf{0})\cos(A) - (\textbf{-1})\sin(A) = \sin(A) So, option B *is* equal to sin(A)\sin(A).

STEP 7

We're looking at cos(90A)\cos(90^\circ - A).
This reminds us of the **cofunction identity**: cos(90A)=sin(A)\cos(90^\circ - A) = \sin(A).
So, option C *is* equal to sin(A)\sin(A).

STEP 8

We have 1csc(A)\frac{1}{\csc(A)}.
Remember that csc(A)\csc(A) is the **reciprocal** of sin(A)\sin(A), meaning csc(A)=1sin(A)\csc(A) = \frac{1}{\sin(A)}.

STEP 9

Therefore, 1csc(A)=11sin(A)=sin(A)\frac{1}{\csc(A)} = \frac{1}{\frac{1}{\sin(A)}} = \sin(A).
So, option D *is* equal to sin(A)\sin(A).

STEP 10

Options B, C, and D are all equal to sin(A)\sin(A).
Only option A, which simplifies to sin(A)-\sin(A), is *not* equal to sin(A)\sin(A).
Thus, the answer is A.

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