Verify the identity. cos quanity x plus pi divided by two = -sin x

Mathematics

1 answer:

7nadin3 [17]4 years ago

4 0

Answer:

see below

Step-by-step explanation:

cos ( x+pi/2) = -sinx

We know that

cos(A + B) = cos A cos B - sin A sin B

Let x = A and pi/2 = B

cos x cos pi/2 - sin x sin pi/2 = -sin x

We know cos pi/2 = 0 and sin pi/2 = 1

cos x * 0 - sin x *1 = -sin x

- sin x = - sin x

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Note:
The area of a circle with radius r is πr².
An entire circle has a central angle of 360°.

For the sector with radius = (3+4) = 7cm and a central angle of 120°, the area is
$A_{1}= \frac{120}{360}*(49 \pi ) = \frac{49}{3} \pi \, cm^{2}$

For the sector with radius = 3 cm and a central angle of 120°. the area is
$A_{2}= \frac{120}{360} *(9 \pi ) = 3 \pi \, cm^{2}$

The area of the shaded sector (see the figure) is
$A=A_{1}-A_{2} = ( \frac{49}{3} -3) \pi = \frac{40}{3} \pi \, cm^{2}$

Answer: $\frac{40}{3} \pi \, cm^{2}$