How Accurate Are These Trigonometry Compound Angle Calculations?

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will.i.am2
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Verify the compound angle formulae for;

a) sin (20° + 30°)

sin(A + B) = sinAcosB + cosAsinB

sin(20°+30°) = (sin20°)(cos30°) + (cos20°)(sin30°)

0.76 = (0.34 x 0.87) + (0.94 x 0.5)

0.76 = 0.29+0.47

0.76 = 0.76


b) cos (30° + 40°)

cos(A + B) = cosAcosB - sinAsinB

cos(30°+40°) = (cos30°)(cos40°) - (sin30°)(sin40°)

0.34 = 0.87 x 0.77 - 0.5 x 0.64

0.34 = 0.67 - 0.32

0.34 = 0.35

Can someone please verify these answer for me? as I am not good in maths so I just wanted make sure if i had done it right or do I need any changes?
 

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