Here, Cos75º
= cos (45º + 30º)
= cos 45º .cos 30º - sin 45º.sin 30º
= \(\frac1{\sqrt2}.\frac{\sqrt3}2-\frac1{\sqrt2}.\frac12\)
=\(\frac{\sqrt3}{2\sqrt2}-\frac1{2\sqrt2}\)
= \(\frac{\sqrt3-1}{2\sqrt2}\).
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Find the value of Cos(75º) without using calculator or table.
Here, Cos75º
= cos (45º + 30º)
= cos 45º .cos 30º - sin 45º.sin 30º
= \(\frac1{\sqrt2}.\frac{\sqrt3}2-\frac1{\sqrt2}.\frac12\)
=\(\frac{\sqrt3}{2\sqrt2}-\frac1{2\sqrt2}\)
= \(\frac{\sqrt3-1}{2\sqrt2}\).
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