Proof process of cos cos cos sin sin

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It can be proved by the vector method.

Suppose there is a point a on the unit circle, which represents a vector of (cos, sin), and a point b, which represents a vector of (cos, sin), and is the angle between them.

The product of the OA vector and the OB vector is cos cos + sin sin

It is then defined by the product of vector quantities, which is equal to the modulus of the two vectors multiplied by the cos angle, the unit circle upper modulus is 1, and the angle is so cos( =cos( -cos( cos cos +sin sin

The cosine formula that makes use of the sum of two angles.

cos(π/2-α)

cosπ/2·cosα+sinπ/2·sinα=0+1×sinα

sinα

Suppose that the unit vector a (cos, sin) and the unit vector ruler b (cos, sin) are separated from the kernel by b and a vector at an angle of - then there is ab=|b||a|cos( -cos( -cos( -cos( -cos cos +sin sin The -= in the formula has cos( +cos cos(-

Let the unit vector a (cos, sin) and the unit vector b (cos, sin).

Since the angle between b and a vector is -, then there is.

ab=|b||a|cos( -cos( - can be obtained by bringing in coordinates.

cos ( masking ) = cos cos + sin sin to obtain the sympathy.

Proof: cos2 +cos2 =cos[( cos[( Qiaoqing]=cos( +cos( -sin ( -cos( -cos( +cos( -cos( -sin( +cos( -sin( -sin ( -2cos( +cos( -sin

Summary. cos( 2+2) = sin + proof.

Expansion: Mathematical thinking is the use of mathematics to think about problems or to build and solve problems in the form of thinking, thinking refers to the human brain's generalization of objective reality and frontal indirect reflection, belongs to the basic form of human brain activities.

When = Bynen4; =2.

cos( -cos( 4- Trapped Cave 2) = 2 2cos -cos =cos( 4) = Wang Huiku2 The 2 equation holds.

Proof of: cos (Kei Hao Jing + cos ( -cos cos -sin sin ) cos cos + sin sin ).

cos cos ) 2 -(sin sin ) 2 (cos) 2 [1-(socks slow sin) 2 ]-sin ) Yu Shen 2 [1-(cos) 2 ].

cosα） 2 -（sinβ） 2

So the original formula was proven.