Question

Trigonometry !!!!

Find the value of cos 75°?​

Answer 1

Answer:

${\bf{\green{=>Cos75°}}}$

${\bf{\red{=>Cos(45+30)}}}$

${\bf{\blue{=>Cos(a+b)=}}}$${\bf{\pink{CosaCosb-sinasinb}}}$

${\bf{\green{=>Cos(45+30)=}}}$

${\bf{\orange{Cos45Cos30-Sin45Sin30}}}$

${\bf{\blue{=>1/\sqrt2(rt3/2)-1/\sqrt2(1/2)}}}$

${\bf{\red{=>\sqrt3/2\sqrt2-1/2\sqrt2}}}$

${\bf{\green{=>\sqrt3-1/2\sqrt2}}}$

Answer 2

${\huge {\underline {\bf {\pink {Answer::}}}}}$

= cos 75°

= cos (45°+30°)

= cos 45°. cos 39° - sin45° . sin30°

= $\displaystyle\frac {1}{\sqrt{2}}.\displaystyle\frac {\sqrt {3}}{2}-\displaystyle\frac {1}{\sqrt{2}}.\displaystyle\frac {1}{2}$

=$\displaystyle\frac {\sqrt {3}}{2\sqrt{2}}-\displaystyle\frac {1}{2\sqrt{2}}$

=$\displaystyle\frac {\sqrt {3}-1}{2\sqrt{2}}$

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