Share £405 in the ratio 4:11
1 answer:
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Answer:
see explanation
Step-by-step explanation:
using the identity
cos2a = 2cos²a - 1 , then
cos2a
= 2[ (a +
) ]² - 1
= 2 [ (a² +
+ 2) ] - 1
= (a² +
) + 1 - 1
= (a² +
) ← thus verified