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# C2 Trigonometry Question watch

1. Please could somebody help me out with the attached question?

I'm struggling to work out how to calculate the areas of triangle BCD and ADE as I don't know the angles. Some pointers would be really appreciated!

Thanks!
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2. (Original post by grace15)
Please could somebody help me out with the attached question?

I'm struggling to work out how to calculate the areas of triangle BCD and ADE as I don't know the angles. Some pointers would be really appreciated!

Thanks!
One approach would be to use the reverse cosine rule to obtain one of the angles in a triangle where you know the lengths of all three sides. Then use to get the area.

Alternatively, you could use Heron's Formula. Given the length of all three sides of a triangle, the area is given by:

where ,, are the sides of the triangles and is half the perimeter.
3. (Original post by SherlockHolmes)
One approach would be to use the reverse cosine rule to obtain one of the angles in a triangle where you know the lengths of all three sides. Then use to get the area.

Alternatively, you could use Heron's Formula. Given the length of all three sides of a triangle, the area is given by:

where ,, are the sides of the triangles and is half the perimeter.
Thank you so much!

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