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math help needed

please look at the attachment
triangle pqr.png76.6KB
Reply 1
Avatar for As.1997
As.1997
OP
16
I've almost done it using the sine rule but I'm not too sure how I am supposed to work out sin 45 and sin 60 without a calculator.
Original post by As.1997
I've almost done it using the sine rule but I'm not too sure how I am supposed to work out sin 45 and sin 60 without a calculator.


You are told cos 60 so draw a triangle and find sin 60. You should know sin 45 from the 1,1, root 2 triangle.
Reply 3
Avatar for papie
papie
16
Original post by As.1997
I've almost done it using the sine rule but I'm not too sure how I am supposed to work out sin 45 and sin 60 without a calculator.

you have to learn the exact values of trigonometric function for 3 angles 30 , 45 and 60. you can use the triangle method.
CFD9EC10-3D16-4CDF-9B87-27000561CDD4.jpg.jpeg
Original post by As.1997
I've almost done it using the sine rule but I'm not too sure how I am supposed to work out sin 45 and sin 60 without a calculator.

Draw an equilateral triangle, and a right-angled triangle that is isosceles. Then have a real good look at them. Any half-decent maths teacher should have already done this with you.
Reply 6
Avatar for papie
papie
16
watch this video : https://www.youtube.com/watch?v=6NOZtD2Q6Y0
Reply 7
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As.1997
OP
16
Thank everyone

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