展开 (1+cos(3t))^2

解答

展开

(1 + cos (3 t))^{2}

1 + 2 cos (3 t) + cos^{2} (3 t)

求解步骤

(1 + cos (3 t))^{2}

使用完全平方公式:

(a + b)^{2} = a^{2} + 2 ab + b^{2}

(1 + cos (3 t))^{2} = 1^{2} + 2 \cdot 1 \cdot cos (3 t) + cos^{2} (3 t)

= 1^{2} + 2 \cdot 1 \cdot cos (3 t) + cos^{2} (3 t)

化简

1^{2} + 2 \cdot 1 \cdot cos (3 t) + cos^{2} (3 t) : 1 + 2 cos (3 t) + cos^{2} (3 t)

= 1 + 2 cos (3 t) + cos^{2} (3 t)

e x p an d cos (0)

e x p an d \frac{( x + h ) ^{2} + 1 - x ^{2} + 1}{h}

e x p an d (x - \frac{1}{x})^{3}

e x p an d (2 n)!

e x p an d 3 (x - 2)^{2} + 3 (x - 4)^{2}