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# Area of triangle Watch

With part b in the question which is on the attachment, why can't you do
A=1/2 absinC
120=(17)(17)sinC=120

Thank you.
2. (Original post by krisshP)

With part b in the question which is on the attachment, why can't you do
A=1/2 absinC
120=(17)(17)sinC=120

Thank you.
Ignore me I am dim !!!!!!!!!
3. (Original post by TenOfThem)
Because 1/2 ab SinC works in degrees
THANKS
4. (Original post by TenOfThem)
Because 1/2 ab SinC works in degrees
Calculate, giving answers to 2 decimal places:
The area of the shaded region R.

Here's my working out:
Area of shaded region R=total area of larger sector with arc A1 - area of smaller sector with arc A2

Area of shaded region R=CA1D total area - CA2D area

This wrong, but why? How do you do this question.
5. (Original post by krisshP)
Calculate, giving answers to 2 decimal places:
The area of the shaded region R.

Here's my working out:
Area of shaded region R=total area of larger sector with arc A1 - area of smaller sector with arc A2

Area of shaded region R=CA1D total area - CA2D area

This wrong, but why? How do you do this question.

Well it is wrong because it is nonsense

The is good as that is the semicircle centre M

But then you need to take away the segment (which is the sector minus the triangle)
6. (Original post by krisshP)

With part b in the question which is on the attachment, why can't you do
A=1/2 absinC
120=(17)(17)sinC=120

Thank you.
The equation 1/2 ab sin C for the area of a triangle works just as well in radians as it does in degrees. The problem you have is that, having correctly established that the sine of the angle you are interested in is 240/289, you have trusted your calculator to tell you what the angle is. And it has told you one possible value - but it is not the value you want! Can you see why not, and which of the other values (out of an infinite number of possibilities) is the one that you really want?
7. (Original post by Pangol)
The equation 1/2 ab sin C for the area of a triangle works just as well in radians as it does in degrees.
Me being thick !
8. (Original post by Pangol)
The equation 1/2 ab sin C for the area of a triangle works just as well in radians as it does in degrees. The problem you have is that, having correctly established that the sine of the angle you are interested in is 240/289, you have trusted your calculator to tell you what the angle is. And it has told you one possible value - but it is not the value you want! Can you see why not, and which of the other values (out of an infinite number of possibilities) is the one that you really want?
pi - 0.98=2.16 This is supposed to be the correct answer, not 0.98. I understand why since there are 2 solutions from the sine curve where you get the same value.

THANKS

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