Why is - cos 20 degrees equal to - Sin 70

Why is - cos 20 degrees equal to - Sin 70

4X squared - y squared + 2x-y=
4X^2-Y^2+2X-Y
=(2X+Y)(2X-Y)+(2X-Y)
=(2X+Y+1)(2X-Y)
Find the value of 2sin20 + cos10 + tan20sin10
Simplification of trigonometric function
Original formula = 2sin20 + cos10 + (sin20 / cos20) * sin10
=(2sin20cos20+cos10cos20+sin20sin10)/cos20
=(sin40+cos10)/cos20
Evaluate sin20 ° square + sin70 ° square - cos20 ° square * cot70 ° square * (1 / sin20 ° Square)
Sin20 ° square + sin70 ° square - cos20 ° square * cot70 ° square * (1 / sin20 ° Square)
=sin²20°+cos²20°-cos²20°*tan²20°/sin²20°
=sin²20°+cos²20°-cos²20°*sin²20°/(sin²20°cos²20°)
=1-1
=0
If the square of x minus 4x plus 4 equals zero, how much is the square of X?
Four
2sin20°+cos10°+tan20°sin10°=______ .
2sin20 ° + cos10 ° + tan20 ° sin10 ° = 2sin20 ° + cos10 ° + sin20 ° sin10 ° cos20 ° = 2sin20 ° cos20 ° + cos10 ° cos20 ° = sin40 ° + cos10 ° cos20 ° = cos50 ° + cos10 ° cos20 ° = 2cos30 ° · cos20 ° cos20 ° = 2cos30 ° = 3
sin20°sin110°-cos160°cos70°
=sin20°sin70°+cos20°cos70°
=cos(70°-20°)
=cos50°
Find the maximum value of the square of - 4x + 16x + 7 and what is x equal to when taking the maximum value
-4X squared + 16x + 7
=-4(x-4)²+23
When x = 4, the maximum value is 23
-4X^2+16X+7
=-4(X-2)^2+23
When X-2 = 0, that is, x = 2, the formula has a maximum value of 23
Cos 80 ° cos 35 ° + sin 80 ° sin 35 ° = why do we calculate cos (80 ° - 35 °)
To simplify, cos (80-35) = cos45 = root 2 / 2, so you can see the answer at a glance
sin110°sin40°+cos40°cos70°
Original formula = sin70sin40 + cos40cos70
=cos(70-40)
=cos30
=√3/2