"in a triangular shape" is correct and can be used in written English.
It is typically used to describe the shape of something. For example, "The snowman's hat was in a triangular shape."
Much of her art mixes insects with geometrical forms and the meadow is marked out in six hexagon shapes – inspired by beeswax – arranged in a triangular shape.
Patent 3,508,785, awarded to Fu‐Shueng Chang, de scribes a jointed luggage compartment deck lid that erects itself in a triangular shape if a collision occurs.
In the last year, the smugglers started using bags of homemade spikes —nails welded together in a triangular shape — to blow out the tires on patrol vehicles.
The triangular configuration of the trimeric clusters may naturally result in a triangular shape for the nuclei and thus for the final products.
These extensometers have similar geometries (i.e., three components arranged in a triangular shape) and lengths (~30 m) to the extensometers at ISA, but the distance between the crater and the observatory is <3 km (e.g., Kamo and Ishihara, 1986).
The combination of LST and SAVI by scatterplot results in a triangular shape like LST and NDVI as described by other scholars (see for example Carlson et al. (1994); Gillies et al. (1997); Gillies and Carlson (1995); Weng et al. (2004)).
If it's going to fit in a corner, it can have a triangular shape or it can be L shaped or a more complicated shape that partially surrounds your chair.
It seems that deposit layer profile in the tubing follows a triangular shape.
Fold the circle in half and then in half again to make a triangular shape.
Cut a triangular shape in a wall using a cordless drill.
The suture between the frontals is completely fused [1], and the paired frontals form a triangular shape in dorsal view (Figure 14).
