4cos50°-tan40°

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4cos50°-tan40°
4cos50°-tan40°

4cos50°-tan40°
=(4sin40°cos40°-sin40°)/cos40°
=(2sin80°-sin40°)/cos40°
=[2cos10°-sin(30°+10°)]/cos40°
=(2cos10°-1/2cos30°-√3/2sin10°)/cos40°
=(3/2cos10°-√3/2sin10°)/cos40°
=√3(-√3/2cos10°-1/2sin10°)/cos40°
=√3cos40°/cos40°
=√3